Since I was the one that made the comments on the hand/handle video, I'll comment again. When I started trying to do the full PA pattern, I found myself tilting my hand CCW (about 20 deg.) when inverted and sometimes when upright.
I had a couple of .60 sized models (one still exists!!!) that pulled pretty good. If I flew with my arm extended (using tendon strength), my shoulder would hurt the next day. If I bent my elbow and thus used my bicep strength, my shoulder didn't hurt at all. Pulling the handle up in front of your upper chest gives this, plus a better view of the lines and plane, I think. Ted and Brett say so, anyway. They also explained why we should try to have the handle vertical when flying upright, at least. The 'flat handle' when inverted may be impossible to relearn, but I'm proof that it's possible to tune out the 'minor tilt' thing. That's good enough for me. If for no other reason than your flying buddies can eyeball your handle while you're flying and tell you that you're flying with some "up" or "down" input. Fix that, and your flying generally improves dramatically.
When I was flying my SV-11 (yes, still exists), I found a comfortable neutral, and could get both upright and inverted level at reasonably the same altitude. What I couldn't do was control the takeoff...it always leaped into the air after a short roll. Pete P. and Mike H. both told me to adjust neutral, which I thought was nuts. Finally, after a month or two, I changed a line clip 1/16" to see if it would work. It did, very nicely. Wowzir!
Tho I can't recall what plane it was, I noticed that for one plane, I tended to put my thumb on the top of the handle only for outside corners, and decided that it was an indication of something wrong with the plane. I am pretty sure it was that the outsides tended to be bigger than the insides, and a perceived need to use more input on outside corners. We know that's a trim problem that needs a little work, so get after it.
Some may poo-pooh the handle, the handle position, the grip, the handle weight, and all that. But I'm here to tell you that it makes a big difference, and if you really want to improve, you need to get it right, not learn bad habits, and make notes on the information that Ted, Brett, and other "Top Gun" fliers share with you. I am an Advanced flier that enters Expert mostly, but not all the time. I do too much "arm waving" while flying, but at least my handle is straight up & down for both upright and inverted. I think airplane trim is part of that problem, too. Trimming includes everything from the handle to the outboard wing tip, and should be a never-ending process. Just make sure you can get it back to where it usta was.
Steve