Right, last little bit.
I glued some ceramic paper insulation to the inside of the engine mounting to avoid getting the inside burned by the hot engine parts. Then I fitted the engine and connected the vent fitting and closed it up.
Using my Xicoy CG weight and balance gadget I found that with a 2650 mAh lipo fitted the all up weight (landing weight with full UAT and a little in the main tank) is 3.32 kg (7.3 lb) and the CG is 11 mm (0.43") ahead of my target calculated point. I was aiming for 55mm ahead of the main wheels and ended up with 66mm.
I think I'll fly it at that and then consider a lighter battery or moving the battery back to just behind the Rx if I want the CG further aft.
I started with my heaviest battery, a 5000 mAh right forward and it was very nose heavy.
The engine manual recommends a "2S LiPo or 3S LiFe >1000mAh" but 1000 mAh sounds a bit light to me, but I might try a 2200 with a high "C" rating.