Has anybody here made their own Devano style rising cards? I'm wondering what is the best source for weights and if you did anything to reinforce the two holes for the thread. Thanks!

Maybe some of the tungsten weights used for Pinewood Derby might work well if you can get the right size. The farther it falls the more it will rise, so a small dense mass is best. I've heard of people using lead metal as a mass - maybe a few pieces of 1mm lead roll stacked together would suffice.
Not sure if the holes are reinforced but the card might be a double, glued together for strength

Also copper heatsinks come in 10mm and 15mm squares, might find the right mass there
here's an ebay listing for 20mm tungsten squares, super thin, might be possible to stack a few, but it won't fall very far
https://www.ebay.com/itm/1x-99-95-High-P......LVZVsacb