Muscle Imbalance

What are some decent ratios for Chest/back
strength and quads/hams strength maybe a chest rotator cuff ratio would be helpful too.

I was going through previous issues and saw the Poliquin article “Achieving structural balance” it said 1RM supinated chin should be only 81% of a 1RM close grip bench press.
If this formula is right I have a huge muscle imbalance favouring my back. My 1RM for a close grip bench press is about 110or 120 kgs(245-265lb)but I can do 3 chins with my body weight (82kgs or 180 lb )and additional 60 kgs or 135 lbs. Any way my point is that my 3RM supinated chin is 130% so my 1RM would be even higher this worries my as it is alot higher than the 81% which is supposedly balanced. And if the 81% figure is right not many people should be able to do a single chinup?
Its not as if I have a week chest either my regular bench 1RM is 132 kgs (295 lb)
Please help with advice on if the ratio is right and if it is what I can do to fix it.

remember, those were upper body strength ratios in elite athletes, who could generally bench over 350 pounds, so doing an 81 % chinup with a bench like that is signifigantly harder.