foam archery target

[2012_taco]

This may have been posted before but i am looking to make myself a stacked foam target and i am having a hard time finding a cheap source  to get 1/4" foam pieces. I would like to use the sheet type of foam probably used for packing/shipping. i plan to sandwich it between boards similar to the targets made with cardboard posted on this forum. My thinking is that the foam will hold up better to broadheads than the cardboard, maybe not,  and the foam should be lighter and hold up outside better side.  Any suggestions where I might find foam? Does any one know how the cardboard targets hold up to broadheads? 

[PREDATE]

If you're serious about making a quality target, you could hit Home Depot and pick up a few pieces of rigid insulation board. You'll also want a good/tough sheathing to hold it all together, like maybe a few layers of carpet on either side and between the boards. Then wrap it really tight with a wooden frame made out of 1 x 6 boards. Then you can build a frame for it to stand/hang from out of PVC pipe.

Packing/shipping foam will crumble. The rigid insulation will break, but not nearly as much. We use rigid board for knife throwing