As someone who didn't gain erogenous sensation in my phallus after Phalloplasty, I'm grateful for the size I had pre-op and feel that has made a positive difference. I didn't pump though so I don't know if that would help. It's exceedingly rare to lose the ability to orgasm after Phalloplasty, and if you're going for radial forearm, I'd say that embarking on a pumping regimen isn't necessary.