Thank's for the anticipation
So, I dropped my proposal to my male companions: Let's try to convince these ladies to get naked. I suggested we'd get their confidence up by letting them win the next two matches before one of us suggesting strip volleyball. I also proposed that one or two of us should act prude and be a bit against it, to see if we could bait some of the girls to vote in favour.
On the male side of the net we had one japanese guy, three americans of indian, chinese and european origin plus a brit and me. Two of the americans (the chinese and the indian) were a bit sceptical but mostly on the grounds they didn't really think the girls'd actually strip, so we quickly decided to give it a try.
So, when the girls came back we proceeded according to plan.