USGA, Plus AGA:
AGA players can compete equitably with USGA players, simply by using the same chosen AGA equipment and rules consistently. Some players will use USGA equipment and balls, but select a few rules, such as tee it anywhere and one mulligan per hole. Others may select several clubs and balls to augment their equipment, while using all AGA rules.
Once you have settled on the rules and equipment, then, just like USGA, your scores will adjust accordingly, allowing you to have more fun and also play with other AGA or USGA golfers. That’s the beauty of the USGA handicap system; it will adjust as your scores improve, as long as you apply your chosen rules and use the same equipment consistently.
Many AGA players also play USGA golf. We suggest dual players keep two USGA handicap numbers to separate the games. Or, you can just keep your USGA handicap officially, and calculate your unofficial equivalent for AGA using an online USGA index calculator.
While the USGA system will adjust for AGA improvements, it is just too complicated and it penalizes you in the way it is calculated. What you think is your average score and target is actually what you would expect to play to in fewer than 10% of your rounds. That is a very tough target, and adds to the frustration of the game.
As an alternative, just use an arithmetic average of 5-of-7 rounds (thawing out the highest and lowest of the 7). For example, if you play 7 rounds of 97, 108, 101, 93, 98, 99, 103, your AGA target is (97+101+98+99+103 divided by 5 =) 99.6.
Again, the key to playing competitively is to be consistent once you pick your rules and equipment. Remember, the pros are using illegal equipment too -- their highly trained minds and bodies. Their scores reflect that to such an extent, they no longer have a USGA index.