I also use pure silicon grease( used to be called titration grease) and put a light coat on the stopper before final assembly
I'm starting to read more and more post about adding extra sealants to certain parts of the engine bottle etc.
My question is Shouldn't the parts you buy be free of manufacturers defects ? and if they are not should'nt you be getting your money back IMMEDIATELY ?
See if every one just keeps on fixing things bought from hobby distributors (or adding things to help secure plane or parts ) then I feel we will never never never EVER be able to buy something and trust it was made suitable or reliable for the most picky RC hobbiest.