Over at Ikea, they sell the perfect sized stools for your candy cab gaming needs, the Marius which is only 17 3/4" in height:
http://www.ikea.com/us/en/catalog/products/10135659/
Add a handy cushy pad to place on top of it and it'll definitely mold to your bottom indeed. Over the years, the Marius stool has been sold under different names and slighty different styles but sized just right height-wise for your candy cab(s). Some time back, Target used to sell those cool foldable cushioned 17" stools with a handy back brace for leaning back on (for extra back support)...those are worth their weight in gold.
For the ultimate gaming stool, there's none better than an original Japanese gaming stool (i.e -- Taito's own leather gaming stool comes to mind) like those seen in them world-famous game centers like HEY! and the like. Every once in a great while, a sale thread will pop up for an Japanese gaming stool which'll sell out like hotcakes. Add a complimentary "stolen" game center cigarette ashtray + a proper Japanese gaming stool = the best way to be gaming in grand "candy cab" style.
There was one arcade that I used to patronize back in the mid-1980s and into the early 1990s called Cal's-R-Cade based out of Modesto, CA, that had plently of bar stools for playing in comfort with those Dynamo based woody cabs. Sure beat having to stand up for those serious arcade gaming sessions with a handy cushy bar stool any ol' day.
PC Engine Fan X! ^_~