The temps I recorded on mine, in an earlier post shows in-cowl and without. I also had the temp probe right under the exhaust outlet (well, one fin down anyway)
I would suggest that the 377F that MDavis got is way too high. Perhaps with some baffles in place, and sufficient exit area, this could be controlled fairly well. I think the interesting thing to me is the way the temps fluctuate from high to low, and back again, might be a cause for concern on the metallic makeup of the cylinder..perhaps contributing to the failures.
I have installed 3 small louvres, one above and behind each cylinder, and two large ones in the rear of the cowl, to aid airflow OUT of the cowl. I am also going to install a baffle, made by these guys...
www.rcmodelcomposites.com
I will pick it up while I am in the UK and will start testing in May again..