RE: OS 160 FX / Bisson Pitts / Perry VP-20 owners
None of the parts in your fuel system are made with enough accuracy to make others' number of turns relevant.
Other things, such as length of fuel line to the pickup clunk (which you are aware of), the brand of the fuel line, whether or not the fuel line is an absolutely straight run without any deviation or kinks, type of glow plug, condition of glow plug, type of exhaust, mods to exhaust, blah-blah-blah will destroy any commonality that all of the models may share. This is not to say that it would not make interesting reading. But it would confuse those that haven't managed to load all of these factors into their heads and associate them with their function and effect.
Moving the tank back to the CG is good if your engine is the type that has a robust fuel delivery system built-in. Doing it with third party parts is really stretching it a bit. Engine reliability is more important than making hovering easier, in my book anyway. I'd leave the tank up front and give the engine a break.
The VP-20 pump is not made for four-strokes (other gentlemen). But it was advertised as being good for four-strokes because it did not require crankcase pressure, but it can be used with either type of engine. I'm surprised that you're not running the VP-20 wide open just to keep up with this large of an engine. Oddly enough, you can activate the pump diaphragm in a VP-30 via crankcase pulse pressure, as long as you install a tee and run a piece of fuel line as a vent line for about 4" after the tee. The latter information came via Paul McIntosh of RC Bearings fame. Sorry for butchering your last name so many times in the past, Paul (I know you are out there!). I was raised with some friends by the name of McIntyre and I can't keep you two straight.
Happy New Years, everyone
Ed Cregger