HELP! Anyone Working with Acrylic on Vellum?: How do you stop it from WRINKLING???

[~Memory~]

Hey everyone. I need some help or some friendly advice from you guys.
I've cross-posted this in the Acrylics forum as well, but I'm trying to cover some ground here for those of you whom might not browse that forum. I'm stuck, and I am REALLY in need of some advice/assistance.

This weekend I went out and bought some synthetic vellum. I have never used vellum as a painting ground before, so I was pretty much in the dark in a new world when I delved into it today and attempted to paint on it.

This pic I've posted is a 5" x 7" with fluid acrylics and ink. I plan on painting it on canvas later, but I thought it would be a good subject to start on vellum with.

HA! I was so wrong. The reverse painting technique I used, which is working on the reverse side going from the foreground to the background turned out okay, (it could have been better, but I'll get used to it sooner or later) but the biggest problem was that the vellum wrinkled----badly. You can see it in the scan.

My question is, do you have to treat vellum in a way like that of watercolor paper, maybe? Would you have to size it before you painted on it? I have absolutely no idea as how to keep this from wrinkling. I didn't water down the paint, so I couldn't have saturated it too much, could I?

I am two seconds away from layin the painting down on a table, throwin a handkerchief on top of it, and straightening it out with a curling iron...lol The reason I say curling iron is because it doesn't get as hot as a clothing iron and I know that vellum scorches easy. But as unconventional as it is, it probably won't work either.

I am seriously at my wits end on this. If you can lend some advice or ideas even, please do, because I really like this technique and it would be a shame that I have to lay it down because I have to chuck every single piece I do because it wrinkles.

Maybe I could make lemonade out of these lemons I've been handed and work the wrinkles in to my advantage.....Can anyone say mixed media collage? LOL It'd be some great texture anyway, a happy accident if you would. Plus, I've got some papers and things I've been absolutely dying to find a reason to use, so maybe that would be the route to go. Please help.

Thanks for looking and the help you guys!