4-blade Pawnee Performance?

Can anyone out there with experience behind both 2-bladed and 4-bladed
Pawnees give me an idea of what the performance losses are?

My club has debated this off and on, but I was recently at a field
with a 4-bladed Pawnee and was much impressed with the lower noise.

Problem is, I've got club members claiming that it'll cost over $10k
to do the job, and we'd give up 25% to 30% in performance due to the
extra blades.

Can anyone corroborate those numbers?

Thanks, take care,

--Noel