Although a nice 1892 Silver dollar would probably work, you are right about the cost efficiency issue! Interesting how you put a double-sided heatsink on the flex. I'll have to try it. Never noticed that both sides can get hot. Is that really a fact?
That's a lot of current to be pumping into it. My next build is in process as we speak for a similar MXDL, as soon as I can find a way to cut a piece off a solid copper bar.
If you are running an A130 diode, it may be pumped a little high, I'm not sure how much they can take, but the A140 is rated at 500 more mA than the A130.
I recently removed a red that had a burn mark in it. After hooking it back up, it fried soon after. I think the mark was there for quite some time, and the higher mA is what really fried it.
Hey, cool build and good luck!