In addition to cleat position, you might also look at sole stiffness. The first time I ever got hot foot was during a very hot double century last year. I had switched to a carbon soled shoe shortly before that ride. It happened again on the next double I did - moving the cleat back then helped a lot. (I basically got the the rest stop and threw my shoe at DH begging him to move the cleat back because I was so frustrated I didn't think I could do it myself just then.)

I switched back to the non-carbon soled shoes for any other hot/long rides for the rest of the year and the problem didn't recur.