I run my Spektrum in 12 different cars and have never had a problem once.
I've never had to add a cap to my receiver.
I've never had a receiver short out.
I've never have any runaways.
Crazy part about all of this is that I've never shortened my antenna, I've never subjected my cars to anything that would require radio modification.
Maybe it isn't a problem with Spektrum but all the fiddling you do with it...to get that ever so important .0000000001 of a second?
Just a thought not meant to bash, berate, or offend anyone, just a thought...