I have to agree Cobia. Either you're flying the A-20G because of a deep rooted love of the plane itself (quite common in Aces High) or you are simply flying it as a means to an end. Whatever that means is, be it a specific performance level in a specific category, or the ability to sucker people in, whatever.
If you want 4x20mm as a means to an end, they already exist on other rides. Find out what else serves as your means to the end.
If you just love the A-20G, then you won't need 4x20mm on it because they don't belong anymore than 17,000lb bombloads belong on the B-17G, or Grand Slams belong on the Lancaster.