Encountered this same issue.
Couldn't change animation speed to 30.25 in Ultimate Unwrap... but in theory, was wondering if I could just multiply my start, end frames with the original vs new count ratio.
For example, if my animation contains frames and new gmf file contains frames, then in theory... I should multiply my start/end frames by 6875/5500=1,25 - I might do fine?
To the test pod batman!
--- seconds later
Yay, works! (at least with 2 randomly chosen animations)