Re: R3 vs R4 vs BaseFit
I have trained as many as 5 people at once on my R-3 rack. Just get an extra set of J-cups and make sure there is space enough on both sides of the rack to squat (in other words, don't put it right up against a wall.) I feel the R-3 is well suited here, given that it's narrow and it is identical on both sides. My gym is in my basement and the R-4 would have been too deep to allow this, in my particular situation.
(I have no affiliation with Rogue, I'm just a satisfied customer)