Sounds like your doing all the right things to reduce feedback risk.
Outdoor gigs usually mean a hollow stage, that can be a problem too, with vibration causing feedback issues.
Do it.. jam it behind the tailpiece with a bit of foam, that also helps stop it vibrating as a potential cause of feedback. Used a G75 for years, now upgraded to a Shure.
Buy the Platinum Pro. It does exactly what you need. The Jtone pickup is a cheap pickup, there are many options out there which will improve your sound.