This is the beta to the "Imperfect Impasse". It is my opinion that the best way to perfect pass IS over the top of Whatcom peak though:
After the peak(6534') that is after Easy peak ,there is a descent to 5400". It is best to generally stay high as you can without traversing cliffs. You will eventually do some steeper talus/downclimbing untill you get to a fault/gully filled with snow. It has cliffs on both sides. Descend to a tree on flat ledge. It offers the only access into the "Imperfect Impasse". It has a ledge that seems bad but goes, many rope up .Last person is solo though. the other side is doable but looks tough. It is the only way through.Reversing it is possible by rappel. Dont let it psyche you out ,it is just adventure along the way.w