I have block hugger headers on my car, and also have a SBC. In addition I have the MAD modification to a Ford starter solenoid with battery in the trunk. I have no hot start issues at all, quite the contrary. People have asked me what starter I have because it cranks over so fast. Do not overlook the obvious trying to solve your starter problems. Masking it with shields and blankets is no answer.
There are a myriad of problems that can cause this, the least of which is heat soak IMHO.
Grounds not making good contact
Battery cables not making good contact
Battery voltage not high enough