Good Evening, James,
If you were happy earlier with standard T-Max Developer, give it a try with 4 x 5 film. Notwithstanding the Kodak warning message, you may find that it works quite well with sheet film. Apparently, some users have experienced some kind of deposit or residue problem with the T-Max/T-Max Developer combination; I never have and can only speculate that local differences in the water supply may have something to do with it. Since I've never had any problem, I continue to use the regular T-Max with both roll and sheet film, normally with a 1:7 dilution.
Konical