OM, in regards to my experience in RB;
I generate the tracks in the odd times (switching to even and back to odd without issue).
I think the key is I generate the tracks after the time changes are established, not before.
Therefore there is no 'stretching' beyond the normal generation process..
RB will then just (for example) generate a 4/4 and 3/4 phrase in the song to equal the 7/4 (or whatever), and the user never knows.
After that the generated AUDIO is handled as 7/4 for editing etc.
This is even if the generated track is a 4/4 style; it simply drops a beat (unless you make a part marker that triggers it to generate a lead-in etc.) It can't create what never existed so it figures out how to accomplish the task by simply making sure the '1' happens when it should.
I *think Jeff actually posted this info once a while back.

/maths; it isn't hard at all for computers

I do not work here, but the benefits are still awesome
Make your sound your own!