This stuff is just too inconsistent on results. That first small tube worked beautifully; nothing that I have tried since as come out anywhere near as well. One try gave me a hard resin, but very little stiffness. This morning's try, even after 25 minutes of baking in the oven, is still tacky. I suspect that perhaps the hardener I bought at Home Depot yesterday might be old (although I can smell both the peroxide and the ketones very readily).
The advantage of fiberglass over having an aluminum tube rolled is cost. The materials cost to make these tubes of fiberglass is about $40 each, as opposed to $100 each to have them fabricated of aluminum and shipped to me. The problem is that if you have to make four or five attempts to get an adequate fiberglass tube, it turns out to be cheaper to have them made of aluminum. At this rate, I don't have any confidence that even four or five attempts will be successful.