Keith,
The only proper way to set the tag air pressure is by weighting the coach, preferable making the adjustment while still on the scales. Any excess pressure in the tag adjustment will add too much weight to the front axle, and since most Beavers have very little capacity to spare when it comes to the front axle, you need to be cautious. When you add weight to the tag axle, weight comes off of the drive axle, but some weight transfers to the front, and it becomes a balancing act if you have a very heavy coach. On my coach, i have to run just over 11,000 lbs. on the tag to get the drivers under 23,000 lbs. and that gives me over 17,000 lbs. on the front axle. This leaves me with very little room for compromise as you can see.
Gerald