Belly Casting

Not sure where this belongs, actually!
We did a belly cast last night, and despite the lady in the shop assuring me one pack of wrap was enough, we have more than one weak spot.
My question is, for those who have done one or more, or who have casting experience, do I get another packet and just lay fresh plaster over what we've done, or do we just start again?
Weakest spots are under the bust - we just didn't have enough in the end to reinforce it properly at casting time. I thought that once it had set, it would be dry enough to hold it's shape to put some more strips on. Would it be better if I put it back on, or can I do it on a working surface instead, if it's viable to do this at all?
The thought of doing it again is ok - it was much easier than anticipated :)

You could probably do it either way, I remember using the modroc strips in primary school to make things and if the project was a bit weak in spots, we'd just whack more strips on at the next art class after it had been drying for a while. No big deal.

Thanks, Meo - I'll give it a go :)