HI Rusty, FWIW, yesterday, I took out the thermostat and put the plug back
in (previously tapped)(it is easy to tap, but be gentle and don't go too
deep-- 1/2"NPT).  It took about 45 minutes.  following the same logic as you
wrote:

"I took another look at the hole that needs to be plugged, and it looks
pretty easy to tap, especially now that everything is open, and dry.  I'm
now thinking that I'll try the engine first without the thermostat, since my
first runs are going to be on the ground, where cooling will be marginal
anyway. If all goes well with the ground runs, I'll make the first flights
without the thermostat as well, and hope for the best.  Again, I'm trying to
avoid overheating on that first climbout, when the workload will be pretty
high already. "

Tommy<>< waiting now for two new injectors