40 deg would be pointless. You could virtually ignore the heat damage while using 2 simultaneous SCBs. And ignore heat sink and hull reinforcements in the process. This would basically be 1.4 magic potions all over again. Now if you want your potions you have to coat your stomach in peptobismo first. Using heat sinks + SCBs in a 1:1 ratio.
It basically means that if you want to be able to fully recharge your shields with 2 SCBs without taking heat damage, you need to sacrifice 2 utility slots to heat sinks. Which means that your shields will miss out on the +40% from boosters, but they will still be 3000% stronger from SCBs,
if you can avoid dropping shields. It's a risk/reward situation.
OR you can opt for the fast regen shields and hull reinforcements if you want to be tougher naturally without resorting to risk of dropping your deeper SCB shields with an average strength hull. So now we have real choices in how to loadout our ship for different types of tankiness.