Any ideas of how to hold a pumpkin in a pumpkin launcher?

Today my friends and I made a pumpkin launcher that is going to launch a pumpkin between 4–8 pounds. We have the whole thing constructed except for the pouch or holder that is going to hold the pumpkin. I made a model of it in Google sketchup before building it and I will put a link to it. But does anyone have any good ideas of a container or some way to hold it? We have thought of just a piece of leather but we do not know where to get a piece of leather large enough. Or a colander but we think that the colander is going to bend. The lines in the sketchup model are actually bungee cords. The stick near the back is going to be a bench press bar. I dont need to explain everything all I need is an idea for a pumpkin holder. Also there has to be a way to attach string to the back of this pouch or whatever so we can pull it back and cut it with an axe.

http://i111.photobucket.com/albums/n126/omgthepopo/pumpkinlauncherv2.jpg

this thing is 8 ft tall/long and 4 feet wide so it will fit in the back of my truck if anyone is wondering.