A spacer design for the Duchess Board Game Table cup holders that provides a nice firm support. I was unhappy with how wobbly the cup holders were so I designed a spacer that allows the cup holder to be tightened snug. It's also designed to stay in place by centering on the little screws that hold the metal bracket to the cup holder. I just made them so we'll see how long it stays tight, but they don't wobble anymore!
Selling them here if you don't have a printer: http://www.ebay.com/itm/-/142477757465?
I used 1.6mm wall thickness and 0.8mm top and bottom. Used FreeCad to design and Cura to slice.