One more thought:

I think most of the guys who were running these engines on 30% nitro back in the day were adding an extra shim to the head to lower the compression some. It's been a while since I've read the Bolly Book and this may be addressed in there?? I know I've read Troy Newman and others mention it. I haven't added any extra shims running the YS 20/20 fuel. I don't think it really becomes necessary till you get to 25% nitro or more. Hypersensitive needle adjustment, blowing glow plugs, overheating, sagging under load in climbs, harsh/lean running despite taking off with a good needle setting; Those are all symptoms of too short pipe length, apparently too high of compression will exhibit similar symptoms...

Please keep in mind I'm no expert!! I'm just passing along stuff I've read or learned from others and maybe a little bit of my limited experience mixed in...