Will continue with the build shortly, but wanted to post a performance update.
I have the 280 kit in it, along with some porting and another minor jetting change. Starts MUCH better, 4-5 kicks when cold, 1-3 when warm. There is still a small bog when transitioning from the idle circuit up onto the main. I need to dial this out with the AP bleed, but I was having so much fun that I did not bother.
New top end is broken in. The bike now has a smooth, steady power that works when you are precise or sloppy. Rode with a skilled rider on singletrack on a KTM450, and keeping pace was not hard. It is like a small electric motor.
The biggest improvement was the suspension. I don't know how, but my settings were all screwed up. I was at 17 clicks out of 23 both on all three settings (did I sleepwalk?). Reset to 7 on compression, 10 on rebound, and now MUCH more controllable - night and day.
Biggest observation is how competent the bike is on tight singletrack with direction changes. I switched with my friends 450 KTM, and although that bike feels more impressive, it is easier to go fast on the 250 because of the wheelbase and easy power. The biggest reason is how un-taxing the packing is mentally. The suspension still leaves some to be desired, but there is potential and I already have a CRF front end in the works. At that point I will hopefully be where I want.