Behind-the-rack break shots are my favorite, too. I'd practiced the behind-the-rack break shot a lot, especially the one where you use inside english to pocket the object ball, glance off the back of the rack, and spin-out three rails to the center of the table.
While yes, it does push balls up table, it's pushing them into open space. You have less of the "balls colliding into each other" thing as when -- e.g. side-of-rack break shot -- you're pushing the balls around in an already-constrained area of the table (i.e. the foot of the table). I don't worry so much about shooting balls uptable or having them up there, because like the rest of us (most, but not all of us), we practice other games besides 14.1, and are used to having to deliver on what would be considered a "tester" or "risky" shot in 14.1.
I was really glad to read Lou's trip report from his lesson with Ray Martin, because it confirmed my already-held belief that behind-the-rack break shots almost never fail to give me another shot.
Interesting outcome of practicing that "inside-english-to-spin-out-3-rails-to-the-center-of-the-table" behind-the-rack break shot: when using this technique on standard side-of-rack break shots (but with a modification -- low-inside english on the cue ball instead of high-inside), the cue ball spins out to center of the table, rather than staying down there, possibly getting stuck to a cluster or to the pile. Yes, it does take some practice -- many find inside english a tough nut to crack -- but the result is worth it, IMHO.
Good thread,
-Sean