I do not fly HPR, but I'm guessing 25 grams is the most that you are allowed without being declared a DD. I suspect a few HPRs could survive 25 grams, while others should contain a self destruct package for safety!
I prefer the electronic flashers to pyro solutions. Back in the day (or twilight as it were), I built and flew an SAI Blinkin' Beacon. It worked, but but the parachute settled over the beacon. and I had to wait till morning to find it in knee high corn. These days, I think a flashing LED Christmas light bulb and battery would suffice. Although a super bright LED or Xenon flasher would be better.
We had a club member who was our resident Enerjet power freak. He had a nasty habit of launching flash powder in paper MRs. I don't know any of the details, except that his rockets survived. So flash powder maybe, 4F never. If you are going down the pyro road, you might take a look at military signal and illumination rockets.
