Well I just made up some CFW yesterday (4 x 20l buckets) 1st gen, and after mixing the cooked Cornies with the hot sugar solution and topping up with cold water, the temp was at 45 C.
I let it sit until it was time to close up the shed and put the dogs away, and get dinner sorted, (6ish) but because it was a nice sunny day today the temp wasnt dropping in the shed, or the buckets, very much. I pitched the yeast (Lowans) at 40 C anyway. My thoughts were that if it failed I could repitch in the morning and there would be some extra nutrients in there as well. But Lo and behold, I have 4 nice frothy buckets this morning! Not suggesting that everyone try this or that its not damaging but it seems that Lowans, at least, can tolerate a little bit of extra heat.
Cheers Phil