I've arrived late to the show, but I'll add my two pennies.
To answer the original question Jerry asked, I use seedlac as a sealer the same as Tallbear. I apply a heavy coat until it won't take anymore, then wipe away any excess build-up with a damp rag of alcohol. Virtually any finish, including BLO, can be applied over this.
As to Permalyn - I think as with any finish it requires the right technique to make it look good, but Bill Shipman and a few others I know sure know how to make it look great! I've used it occasionally as ONE thin coat over a home-brew BLO varnish that was being stubborn to cure fully, and WHAM, it was entirely dry the next morning - I keep it on the shelf just for this purpose.
I won't go into elasticity or durability as I've not done any proper tests of it. I'm not a fan of how clear and runny it is, but that doesn't mean it isn't a good finish.
-Eric