Thanks, everyone... I called my vet yesterday and asked sme questions, and they strongly urged me NOT to shave him, because the fur helps to control his body temperature, which means keeping him warm when it is cold AND cooling him off when he is too hot.
(Even though I mentioned he is indoors-only, she kept going on about how he could get sunburned. I repeated that he is an indoors-only cat, all my cats are strictly indoors only, and she STILL lectured about the sunburn factor, I started getting annoyed... but that's neither here nor there, just irritating - woman, please HEAR ME, how many times can I say this? Ahhh!)
Anyways, I will regulate his play time and watch he doesn't get too stressed, offer lots of water if I see him panting, and keep freezing towels for him to lay on in the hottest weather. Does anyone else do this for their cats? Soak a dish towel and lay it out in your freezer, once it has frozen solid, you can bend it to make a tunnel (Cage climbs under the tunnel and crouches there like a little King, Cash prefers them laid out flat so he can stretch out on top and snooze, he always ends up being very damp, Cruz won't touch them). It's easy and free and really cute to see.