Yes,I have and DO machine my own hubs and I have been in the engine test stand buisness awhile now and have quite a bit of experience messing with these engines(mostly glow I admit). Although I will gladly admit to not being the most experienced hub maker ever,nor will I be. I didnt mean to offend anyone either. I also dont know what aluminum I'm getting from the machine shop as it doesnt really matter for the way I make my hubs. Not saying the others arent worth $20 I guess or wont work......just stating that its possible to get alternative hubs cheaper I suppose. I dont know how much t-6061 would cost in material,but its really not that hard nor does it take that long(couple hours maybe) to produce a simply hub design like that. Here is some pics of a hub I quickly turned out a couple weeks ago as a simply make-shift hub(you may have read my other post) till my EI got here(which uses a different hub) that utilized the flywheel just so I could run the engine. Theres a couple dollars in material and maybe 2 hours machining. It serves the same purpose of those $20 hubs(flywheel use),but uses a steel coupler that both holds on the flywheel and the prop and I had no fear of stripping anything and it worked awesome! And because making this stuff is simply a hobby and not a business.........This setup would be worth like $15 or less and I think its a tougher hub. But,thats just my opinion honestly. Here the pics....the face isnt knurled yet,nor is the threaded stud cut off because I just threw it together.

I almost forgot a add that short shaft hubs (long shaft hubs are easy regardless) that are designed for EI use [can] require ALOT more labor and would be worth paying 25-45 dollars for a good one. Cutting the proper taper is the hardest part usually [:@] And this doesnt apply to these simply flywheel hubs which is also what makes them easy to make.