Try sticking with the PVC but using a steel pipe core inside it next time instead of shaping it solo. The real issue is that you pushed the heat gun too hard and didn't brace the pipe while it cooled, PVC warps if you look at it funny. Foam and wood flex too much for a heavy greatsword, so you'll get a floppy blade that bends when you swing it at a con. A solid PVC build with a core can take a beating and still hold its shape for years, that foam will dent and peel after one weekend. You quit too fast after a bad first try, and now you're stuck with something that looks fine on a shelf but fails in action.

Ugh, the three whys would absolutely wreck my life. I tried it on a bag of frozen fries once and by the third why I was like “because I’m sad and it’s Tuesday,” which technically held up, so I bought them. But then I applied it to a $15 extension cord and ended up sitting in the dark for a week because I convinced myself I could just charge my phone in the kitchen. My brain is too good at lying to itself to trust any filter that sounds that logical.