Is a rwd t5 cosworth prop single piece or is it 2 piece with the donut ring?

I'm guessing the donut is to help in not breaking props with hard launches big power etc,?

Reason I ask is I'm building a t5 gearbox and cosworth powered car ATM, going for 400 horses...... Need to make propshaft custom size, would you 2piece it or single? it's gonna take hard abuse?
Another q, I've got the axle end flange, need the t5 end, was it only cosworths props that fitted these t5 boxes?
Cheers pics would help