CWK
Contributor
I do both. SDI solo course emphasises redundancy virtually everywhere. Not the SPG, that's just my OCD kicking in. Also, it allows me to check the tank pressure and take a few breaths without turning my computer on until I splash, and should the transmitter fail, I can continue the dive.
No worries. Every diver is entitled to carry whatever gear they like. I’ve seen divers with one regulator attached to their pony, plus a primary regulator, an octopus, and an air 2 attached to their primary tank.