Well I am a Jack Knife (sometimes Cannon Ball) side sleeper. Primarily right side followed by left with a smidge of back sleeping (actually don't like it for long). Funny thing is in my WBBB and Traveler I sleep on my back with no complaint (I dunno why) and can side sleep in any position too (except stomach). As to the knee thing I found that if my hang angle is right and my feet are elevated 8 to 10 inches (plus foot adjustable webbing longer than head) all is good. YMMV
PNW folk are planning group hangs regularly...maybe attend one and try out some different hammocks.
ditto to what LD said.. I sleep on my right side in a WBBB in a jack knife position. at time I'll use a shirt to put between my knees or just use part of the quilt.
Yes, feet have to be elevated for me too.
My back has never felt better in yrs since sleeping in a hammock.