Re the operating angle, in an ideal world they say 5 degrees but back in the Scottly's VW van days we used to run them on everything that moved, such as rally cars and hill climb cars and as they were custom fit ended up at some weird angles.
I never had any problems that float levels or fuel pressure didnt fix.
I would be comfortable running at that angle, not sure about the impact on the G's your chair generates? ............. if you have fuel surge problems just put a slower jocky on board
or fatter swinger
For a mate I am fitting up a cb sohc 1,000 cc engine into a lateish yamaha delta framed 750 at the moment for a drag bike and it has the 14 deg ports. I'll take some pics on the weekend as I have to mock the engine with mikuni smoothbores to see if they fit in between the frame rails, I can put on the webbers for a look ?
cheers