11x7 goes well on low end 60 size motors.

my guess is with 11x7 you will get less max RPM then with 11x6 or 11x5.
if you insist on 7 pitch or speed then my guess would be 10x7 prop.

but why this speed props on a trainer there is no problem of slow speed flight with trainers, you want it to fly slow and with low pitch and pull up strong from low RPM.