[BerntR]

My own experience? Hmm

It's a little like the lottery. I can tell afterwards if the shot was good or not, but I never know what's coming.

My own best drives are when I have less OTT, steep out-to-in downstroke and instead get a more rounded backswing, extensor action without swaying and a loose enough left wrist to get a left arm role thru the ball.(Is that the same as horizontal hinging?). And swing thru to a full finsh.

Sometimes it works ok and sometimes not so ok.

When you say more rounded back swing I take it you mean more horizontal rotation (as oposed to up'n down or vertical rotation). That is perhaps even more important with the driver than any other club.

What about your lower body? Any differentiators there?

You say it's a lottery. Can you judge the outcome of your shots by how the execution felt?