Fleece Problem

We recently switched to fleece and so far I feel it is saving us some time and money. The only problem is that recently my two pigs seem to want to move the fleece up and play under it. So they're in between the crib pad and the fleece. We tried velcro, but it isn't keeping the pigs from going under. They seem to be having a lot of fun. I just don't like the idea of them sitting on where they pee since the crib pad does an okay job but not the best. Plus it seems they no longer pee in their litter box now. I don't know what to do. I was wondering if I should sew the fleece to the crib pad? Any help would be great. Thanks.