Interesting. Perhaps if the foam was sewn in as part of the construction, I couldn't fit enough in during the trip to make a difference.
Another thought is to sew the foam in, and make the sleeve for the belt at the same time, then try each out and go with the one that works best. If the pistol belt didn't work, my next thought was a 2" leather belt.
Life should not be a journey to the grave with the intent of arriving safely in a well preserved body, but to skid in broadside, thoroughly used up, worn out, and loudly proclaiming Wow! What a Ride!