Ethafoam? Really? I didn't see Appalachia as the posters home region
But first -- why not post some pics of what its doing and ask NRS how they came up with the length recommendation that they did.
This sounds silly but if your frame is not strapped down well and diagonally it will slide too and fro causing wear marks especially at the ends of the pipe. Adding an "apparent" 2" to the length of your frame.
If you really want to cut it down and you can spare a few inches of some frame length its real simple to do a clean cut job . First of all you are not from appalachia so put down the axe, hacksaw, sawzall, or pipe cutters
Get a chop saw with a carbide blade. Remove the side rails. Measure twice. Clamp the long keeper end of the pipe down in two places against the table and against the fence. Wear protective eyewear. Dont wear loose clothing. Keep your digits, your dick, whatever, away from the blade. Do a slow cut -- it should cut like butter with a carbide blade without notably dulling the blade (a lot easier on your blade than cutting pergo flooring). When the blade has cut through, release the trigger and let the blade come to rest before releasing pressure and allowing the blade to spring back up. This will keep it from chucking the end piece across the room.
So simple even someone Avatarded with numberous sarcastic posts can do
Hey, if you want me to take a dump in a box and mark it "guaranteed", I will. I got spare time.