I saw the review in this months MAN and it looks great.....
I had at first purchased a TF Cesan 310 twin, but due to a poorly fiberglassed fuse (this is really the best part of that plane as it looks stuning when it doesn't have defects)
I sent it back.....
I am glad that I did becasue now I have the option to get the TF b-25!!!

I have a pair of .91 4-stroke magnums.....
these weight the same as the .70s (execpt when you compare the budget version of the O.S .70's) But I would not purchase a 4-stroke that does not have rings in it.... JMHO
Anyway, is there a size diference between the two??
Perhaps the .91s would stick out further? I guess if they weigh the same I would always rather go with the larger of the two due to engine out experience...... But perhaps having a too large of engine in a 1-running condition isn't a vary good thing either? I may put you in a spin???
Perhaps that isn't much of a worry on this airframe....as it has a very effective twin rudder to counter this....