If you believe the issue could be timing related, you can do a real quick test to help prove it:
Duplicate the issue...Get it warm to the point where it acts up.
Then, when you confirmed it's hard to crank, jump out, pull the coil wire out of the cap terminal, ground it to prevent any arcing, and then see how it cranks.
If it cranks considerably easier with the coil wire pulled, then that is a reasonably decent clue less initial timing might take care of the problem.
If it does not crank easier with the coil wire pulled, the issue most likely lies somewhere else. Heat related resistance/voltage drop in the starting system or wiring, or similar.
This is backyard hot rodder kind of stuff, but it usually works.
hth, good luck.