Spitfire Engine Blown Sparky, Kaput

I thought that I was nearing the end of the Spitfire #3 build, but during the engine run-ups the post-crash RCGF-USA 10cc I just didn't like the sound of the engine, and she didn't seem to get up to full RPM/power. I found the following thrust results, average of 3 measures of static thrust, the aircraft weighs 8 lbs dry. Using a Thrust to Weight ration of 0.7, the plane would fly fine with 5.6 lbs of thrust (I couldn't find any other estimate of Thrust to Weight for gas):

14x6x2: 5.4 lbs

13x6x2: 4.2 lbs

13x8x3: 4.4 lbs

She just doesn't sound right. I am not confident the bearings, especially the front one, are okay, and I think she should produce more RPM.

The spark plug stripped, I think it was coming free during these run ups, and afterwards it just came loose, and it wouldn't tighten. I will be sending this engine to Joe Nelson at RCGF-USA to take a look at and see if he can solve the problems he finds. I suspect she will need a new cylinder head and bearing(s), possibly a new spark plug. 

In the meantime I am considering taking the RCGF-USA 10cc from the Sukhoi and moving it to the Spitfire. That engine runs perfectly, is the same exact engine, and would be a simple exchange. When the repaired engine comes back I can put it in the Sukhoi. I am stalling on that because it runs and works perfect in the Sukhoi and I don't want yo screw around with that. Patience...