Total length of my install is 28ft with one booster. For 40ft, I’d do two boosters and blast gates. One about 10~12ft downstream of the glowforge with a blast gate after it, and one about 5~10ft from the exit to the exterior with a blast gate before it. Both boosters about 200~250CFM. I’d suggest use 4" PVC between the long runs between boosters. Or the whole length if you can manage it (except the bit that interfaces the glowforge directly to the inlet, that should remain flex pipe.)
Then wire both boosters to a physical switch with a light. Or you can do something fancy by getting a dust collector switch/trigger that turns on a load when it detects a load.