Hi Gary

 

For a thick buildup that will have to take some abuse, use milled fibers of glass or carbon mixed in epoxy.  This is a LOT stronger than microballoons.  You couls also build up the corner of the door with a lot of tape,  laminate some fabric around the corner and squish inb so putty underneath.  I wouldn't use BID though since you aren't getting continuous structural reinforcement.  Use 0 degree/90 weave.

 

Dan