Two things:
1) when I bought replacement foam for my Pelican case, I didn't find it excessively expensive. I went to a full feature Pelican dealer.
2) I would not trust any foam that was not cut out to fit the rifle, or the case did not have tie downs. I would be afraid that the rifles could shift in harsh handling during travel when using a foam that relies on friction to hold the rifles in place.
I use a Boyt case that only utilizes friction and have had zero issues on a number of trips.
