We found out that
The 2720z firmware actually has strange references to 1440p, like 1920x1440 (!) and 2560x1440 and 2560x1600 (!). The XL2411Z also has these listed.
When I updated to V4 firmware on the xl2720z, when I used a 1502 vertical total at 100 hz refresh rate, the factory service menu (the one with the burn in and VGA color settings, not the other service menu with the strobe duty/strobe phase/single strobe settings), reported a 1280x1440 (!)@60hz refresh rate from the monitor scaler!
This actually makes perfect sense.
The default vertical total (lines) on a 1080p screen is 1125.
1502 (VT custom) - 1125 = 377.
If you add 377 to 1080 (the vertical panel size), you get 1457, which is reported by the factory menu as 1440. So the scaler (with a 1502 VT) is doing strobing based on an a vertical panel size of 1440p The physical panel is 1080. The result is, the bottom strobe crosstalk (that thick double image where the frames seem to get swapped) is pushed to the bottom or off screen (since the virtual panel size is larger than the physical panel size).
Of course there's no such thing as a 1280x1440 resolution. But this also explains why, when using a VT tweak, the "display mode" scaling features no longer work. The scaler thinks the horizontal is 1280, so even at 1920x1080, "Aspect" suddenly becomes available (it's supposed to be disabled at 1920x1080), and if you select Aspect, the screen size shrinks to a 1280p screen.
Makes sense.
Using a VT 1350 tweak reported something like 1600x1280(!). Horizontal went higher while vertical went lower..
1502 is the highest VT that will work on XL2411Z/2420Z/2720Z and 2430T. 1503 goes out of range. Not sure why (there is, funny enough, a 2560x1600 mentioned in the firmware, but whatever).
Masterotaku did find some things when testing VT changes in the Nvidia control panel (it's much faster and easier to test custom resolutions in Nvidia CP, since you can test them on the fly, without even saving them; AMD requires you using CRU, saving, restarting the driver with the toastyx driver restarter, and not being at the same refresh rate you intend to test, just in case it goes out of range)
On the XL2411Z/2420Z/2430T and 2720Z, there seems to be a large gap after 1360 Vertical total, where you will get an out of range error with a black screen, and may 'think' that you are at the limits, but in fact, after a big jump to about 1470 VT, you get a screen again (with errors), then another black screen around 1482 VT, then a fully functional screen and OSD control from 1496 VT to 1502 VT, which is the true maximum (about equal to lightboost mode's accelerated scanout).
It may be possible that the 2730Z may have Vt ranges that may work or may not work, so someone will have to do some in depth testing to determine the ranges.
Anyway,
masterotaku on blurbusters calculated that on an 1440p screen like 2730Z, the equivalent of a 1500 vertical total is 2000 VT. So we guessed that the 2730Z should respond to a somewhere "around" a 2000 VT in blur reduction mode and improve its strobing crosstalk performance. But then again, that's a wild guess. If I owned this screen I'd spend some nice time finding out what worked, but...that's your job, 2730Z owners
Can you check this for us?
You will need toastyx CRU, AMD /Nvidia pixel clock patcher (MAYBE), the toastyX driver restarter.
First set the screen to 60hz refresh rate, so you don't go out of range on a resolution you are actually running. (if you are using the toastyX CRU, you have to save the refresh rate, so its important to keep the desktop at 60 hz. Nvidia card owners can just instantly test things live, through the Nvidia custom resolution panel).
Then create a 2560x1440 @100hz custom resolution. You can also do this through DVI but you will need pixel clock patchers.
Create a new manual resolution under detailed resolutions in CRU, and change the existing vertical total to a higher value.
Try 2000 just for kicks. The pixel clock should be sky high..
I don't know what the default VT is, so maybe it may have a range of +300-400 from the default.
*BEFORE DOING ANY CHANGES, MAKE SURE YOU SET STROBE PHASE TO 000 in the first service menu (strobe phase = "area" in the OSD. Setting this to 0 should do the same thing).
Save and exit CRU, run the amd/NVidia clock patcher, but BEFORE RESTARTING THE DRIVER, quickly set the refreh rate to 100 hz and test this website at 100 hz.:
http://www.testufo.com/#test=photo&phot ... &height=-1
Set it to full screen and pay close attention to the strobe crosstalk around the bottom.
Then, set your video card back to 60 hz.
Run the driver restarter.
Then set it back to 100 hz during the "test" prompt in your video card panel
If you get an out of range error, just press escape (or wait the 15 seconds) then reduce the vertical total by 100.
If you get a screen, go back to http://www.testufo.com/#test=photo&phot ... &height=-1
and see if the strobe crosstalk at the bottom has moved farther down or off the screen.
Keep trying until you get an out of range screen or no further improvements are possible.
It's very very important that strobe phase be set to 0 before any tweaks are done.
When using VT tweaks, the maximum strobe phase is lowered. Strobe phase at higher than 59 on a 2720Z and 1502 Vertical total will set the persistence to "0 ms" and shut off the backlight.
On 2720Z, the first service menu is entered by powering off the screen, holding button #4 (MENU for 5 seconds) then powering on while holding menu. If the wrong button is held down, the screen wont turn on.
The factory menu (on 2720Z) is enter+menu for 5 seconds. (this apparently is different on 2411z).
I assume that the 2730Z should use the same key combinations.
If you do get VT tweaks to improve the strobe crosstalk (forcing the crosstalk at the bottom of the screen to be pushed farther down or offscreen completely), can you also check if the 2730Z has hidden AMA modes like the V4 firmware for the 2720Z does?
(set blur reduction on, in test ufo alien invasion, then toggle AMA to high or retoggle it (or highlight it and press "back" instead of enter) and then try to see if the ghosting or inverse ghosting on the UFO's or vertical red bar changes or disappers).