Perfect play on a "Jacks or Better 9-6" machine will return 99.54% of your money over the long run. Since you are expected to get a Royal Flush once in 40,000 hands, this is a pretty long run. There are no screws for tightening a machine. The house advantage on video poker is determined solely by the payout with the 9-6 machine as the best, but sometimes are hard to find. Machines with an 8-5 payout are fairly common, but the cruise lines have even less. Most are 7-4, but I've seen 6-4. You also have to be aware of the payout for a Royal. Most are 4000 coins, but some are progressive. Recently on a Princess Cruise, the bar had quarter progressives with a starting pot of $1700 ($2200) by the end. These machines were hardly ever full, but 15 feet away the quarter machines were always full. Same pay table, but getting a Royal there would mean about a thousand dollars less.