I am not a fan of JB Weld but decided to use it for this. My test housing I put the washer on the inside with JB Weld so that if for some reason it did come loose the light would not fall out. After it was done and testing it, there is no way it is going to come off. If you use something other than JB Weld just be sure that it can withstand the heat of the bulb.
This is my only concern with the washer on the inside. I have found some original lenses that were slightly melted from the bulb heat. With the washer inside, the bulb is slightly closer to the lens than original. As good as the JB Weld is holding, I am wondering if I should put the washer on the outside. I may take one of my cracked lenses and put it in the housing and turn it on for a couple hours with a battery just to see what happens. I want to be sure before modifying my NOS ones. Not sure of they make an LED but maybe that would be a better bulb for this?