If you're playing in low stakes games that you're properly bankrolled for, then short-stacking is a bad idea. And yeah, it's definitely restrictive, boring and does not improve your post-flop game. But if you're playing above your ability or bankroll, short-stacking is a good idea (if you're disciplined).

As for FR vs. 6-max, I think SS can be profitable at either. At FR the blinds come around less often but players are generally nittier. At 6-max the blinds will eat into your profit, but you'll probably get called more often.