As I recall, the TX240 is wider than the LT240, necessitating more machining to include compatibility for it. Since it didn't perform better than the LT240, support for it was going to be dropped. Did that change?
So wait, was compatibility for the TX240 dropped? Where does that leave the other thin rads in the 20-28mm range? Do we have current, hard inner dimensions so that no one wastes their time buying other rads? I'm sure it's mentioned somewhere, but I had issues finding hard clearance numbers on the motherboard - floor and GPU - floor. I would assume 40mm & 55mm respectively, but knowing that there were 1-4 more millimeters here or there could open up the possibility of wider radiator support for the 26-28mm radiators, giving people more options to experiment. I completely understand wanting to call it a day at some point with testing and iterating for radiator compatibility, but no harm in providing the inner dimensions to give others the chance to try for themselves. I'd happily shell out to have another radiator or two shipped out to you, even if only for test fitting purposes.
XSPC TX240 = 20.5 x 125 x 278mm, FPI: 22
XSPC TX240 Crossflow = 20.5 x 125 x 297mm, FPI: 22
Alphacool Eisbaer LT = 25 x 120 x 270mm, FPI: 16
Other radiators:
Silverstone Tundra TD02 = 22 x 120 x 273mm (AI)
EK Coolstream SE = 26 x 120 x 280mm, FPI: 22
EK Coolstream Classic SE = 27 x 120 x 273mm, FPI: 16
Magicool G2 = 27 x 120 x 272mm, FPI: 16
Magicool G2 X-Flow = 27 x 120 x 272mm, FPI: 16
Bitspower Touchaqua Tarasque = 27 x 120 x 273.5mm ???
Swiftech Hydrae GT = 27mm ???
Koolance HX-CU720V = 28 x 120 x 276mm, FPI: 30 (AI)
Black Ice GT Stealth = 29.6 x 133 x 277mm, FPI: 30
Black Ice Nemesis GTS = 29.6 x 133 x 278mm, FPI: 16
Black Ice Nemesis GTS XFlow = 29.6 x 133 x 292mm, FPI: 16
Black Ice Nemesis LS = 29.6 x 120 x 278mm, FPI: 16
Edit:
Added
DarkSide LP240 = 27.5 x 121 x 275mm, FPI: 17
DarkSide Cross-flow LP240 = 27.5 x 121 x 291(281)mm, FPI: 17
After digging up the basics on all of the sub-30mm rads I could find, honestly I didn't see any standout winners that weren't likely to be too wide or too long. That said, it wouldn't be bad to know for sure what our clearances were for future products, as well as having other options for people that aren't easily able to aquire the Alphacool AIO.