I have always had good luck with the packer design. Mine is a shelter cloth not tin, but I would suggest a recoat of the shoulder layer with filson wax. I have found that if I wax the cape on my packer early in the season and then again in the spring it keeps me dry. I generally wear a wool vest under it which does tend to keep the coat from hanging directly on my shoulders and back but my well-waxed coat seems to turn more of the rain than absorb it as your seems to.

Get a big can of wax, smear it on with your hands then turn the coat inside out, button it up and put it in the dryer for a few minutes. Do not reveal this to the significant other <img src="/images/graemlins/grin.gif" alt="" />

Take it out warm and put it on and let it cool to form fit.

As an additional note: I generally carry a silicon nylon poncho for wear over my coat when it is really coming down. The waxed cotton does well enough usually, but long duration rain and moderate temperatures generally has me looking to the poncho.

Last time I was out to the Olympic rainforest, I wore my #66 Hunters coat which is double layer tin in the body and single in the arms...I slipped my poncho over it as I knew I would need the extra if I expected to remain dry.

This is my wife in the Hoh rainforest with her poncho over her coat...