Krusty,
I try and do it almost level at 300 mph. How I set it up is the key I think, I have found that the longer you hold the GV in the box the more accurate you'll become. A setup trick, instead of using the view zoom, I have my hat switch forward, set to move the eye position towards the sight and move my head up a bit. On the approach I get the GV in the appropriate box beyond 1.5k, as you get closer to the target you'll have to push the nose down to keep it in the box.
As far accuracy, the best I've ever done off-line (without the dive bombsite) is 10 hits out of 12 rockets, online I've managed 6 out of 12 hits. It is not an easy thing to master, but a single PB1 can kill a tiger. What I've been working on more recently is a way to kill werbie's and osti's from a greater distance.
Also, if anyone's interested I modified a REVI site with the rocket's for a sightly more historical look.
[edit] After rereading your post Krusty I had one more thought. In my opinion the most important aspect for consistent results is speed. I've worked with a few other people practicing the sight and they generally used different dive/glide angels than me, but they also found the best speed for the angle they approached from.