I remove every trace of that tar and use 3M's VHB tape instead and some very heavy 8mil clear vinyl sheeting for windows - works great on older vehicles and a lot easier to get inside the door when necessary . That black goo can start to run in extreme heat and it doesn't come off of anything very easily , as you know . A side note - cleaning it up is one thing I've found a good use for the new ethanol laden gasoline and that's about all it's good for in my opinion .
Sarge
Sarge