I made the decision against sanding down the gel coated side panels. They aren't perfect, however attempting to sand flat for an automotive type finish would likely destroy them by exposing the fibreglass mesh.
So they will do as is, on with the decals.
Also the head gasket seems to be holding after trimming one bolt that was contacting the bottom just as it contacted the washer. I was laying in bed the other night thinking about the head problem and remembered that the 75mm long bolts used were very near the bottom on the two holes checked before assembly.
I did not check all 4 at that time, and sure enough, one hole is about 5 mm shallower than the other three.
I cut all four bolts down to avoid future mix ups.
It's got all of it's power back and more, 135 kmh at hilltop.
This is 10 kmh better than the top gear roll on with the litre sport bike.
It wants to yank the transmission around even with the bolts torqued very tight. It goes back a bit on hard throttle in lower gears then pulls forward on hard throttle in top. The movement is all in the slack in the trans case plus a bit of slack I built into the adjuster block.
I'm going to follow Ludwig's advice and do away with adjustability of the trans.