Howdy,
I am young and stripped of cash. Now that we have that out of the way, let me preach my question. I am going to buy a stages power meter for my bike. I run Ultegra, and was going to buy a compact crank from a guy on my team, new, for $125! But he ran out of them, and doesn't know when he will get more. I was curious, will the sram red drive side crank work with the rival non drive side arm? Stages makes rival meters but not Red.
Thanks, Ethan

they will fit. if the q factor is the same then go for it

You'll be fine as long as the spindles are the same. Red is available in BB30/PF30 and GXP. I think Rivals are only available in GXP.

Yes. But you may need to get the crank arm that corresponds to the BB you have to ensure the correct offset between the splines on the spindle and where the pedal mounts.