Don't bother. Take the middle layer out, throw it up on your shelf over your garage door (more bedding material for me! Score! ) and just throw your weapons inside. The pressure from the top and bottom pieces of foam will hold what you need in place for range trips (Disregard this advice if you're going to fly with your weapons. You will need to cut out foam for them because of the amount of abuse the case will take from the baggage handlers.).Got my RTIC 43" hard case today. I really like it. Its got several layers of solid foam inside so I'll need to cut it out for the shape of the weapon.
My reasoning now is that my weapons can change from time to time so cutting out the foam for every version of them would add up with my having to buy a new foam piece every time.