I'm just enjoying Rudy's dick being confused and he can't figure out why.
The slave thing was a weird turn of events. "I can't learn to create figures so I'll get a slave to do it for me" wasn't what I was expecting. But I suppose if Zanoba just wants figures (without wanting to make them), and Rudy isn't interested in selling figures then that's his only bet.
Given that strength was an issue for Zanoba (only later did they mention clumsiness), the immediate solution I thought of was to have him sculpt large, durable materials like giant statues instead of soft clay.
Addit: Fitz was actually staring at the male slave's crotch the entire time she commented on how big they got. Rudy missed that detail too.