The prop shown below from my 300 sq in Bienenstein “Challenger” has a 14swg piano wire propshaft and a 16swg balance wire,
The same gauge wires are used on the double blade folder seen on page 2 of the Jossien “Le Vibrant” 8oz Vintage Wakefield PDF available here:
14g shaft 16g outriggers.
I find any minor weight penalty here is irrelevant because one invariably has to add weight at the nose and to make a real difference to overall model weight (so they tell me), its the rear end that can be seriously addressed.
Rearward spacers, no. of coats of dope, stab/fin wood selection, rear bobbin choice, blah blah blah