My mini starter developed a slow start when hot problem. I thought it had gotten baked from header heat. So I removed the starter and discovered that the short wire between the solenoid and the main body of the starter had the rubber boot pinched under one side of the ring terminal during assembly. You could see where the terminal was burned from arcing. I fixed that, put the starter back in, and no more problem!
I might look at that if I twiddle that (not-so-)Tuff Stuff starter I used. Be this as it may, I actually prefer a slow starter, as my engine bumps to life VERY easily with an old style, slow starter, but with these damned Denso sorts they always spin the damned thing up, whether its good or not, I replaced the Tuff Stuff one w a PowerMaster which APPEARS to be an old style, permanent magnet Mopar starter, but that's as far as the resemblance goes. Its still a Denso. I'm going to rebuild the original starter that came with our '68, as it still works OK now, but shows symptoms of wear. Bushings, brushes and a good cleaning should put that ancient jewel back into excellent operating condition for future decades.
My main power lead consists of a #2 AWG welding cable, insulated by high temperature, cross linked nylon polymer stuff meant for hard use, with ultra-fine strands to insure optimal conductive surface area. This got crimped a bit for extra mechanical strength, then soldered into a copper lug on each end, and securely attached, nutted and insulated to prevent those possible arcs. A heat shield on the starter also protects the power stud from random conductors shorting it to ground.