I know I am going to hear how I have just made a possible "car bomb" but any car is a bomb when you look at motor oil, fuel, brake fluid etc. I don't consider 12oz of refrigerant to be that big a deal. I used to drive a truck with 3 large O2 tanks and 2 acetylene along with 5 gallons of lacquer thinner and many gallons of thinner based paints and solvents so 12oz of refrigerant is not much of a threat in my book.
I had to rebuild the A/C on a 64 ford this week and after I was finished the 134 just flat didn't work very well. Same problem with the 240d I brought home a couple of weeks ago. It was cold at temps below 90 but sucked at 90+ and the compressor sounded very overworked. Kind of the same deal with the Ford.(both York type) I can buy r12 but at $65.00 can or $800.00 for 30lb bottle it is way over priced. Why give Dupont all that money? So I started to look into the r12a stuff used in Europe and Canada, and legal in 43 US states. Figured I would give it a try and man WHAT A DIFFERENCE! In the 240d I get vent temps of 36, down from 55 when it's 90+. Not only that but high side pressure is down to 150psi, low side is at 28 psi. Same on my 300d. After seeing the difference I had all the 134 removed from it as well and redid the system with 12oz of duracool vs 2.8 lbs of 134a. Vent temps are 37f at 96f outside. I don't feel any drag on the motor like I used to when it kicks on either. Pressures are way down on the 300d as well. 33 low side, 160 high.
Yes the stuff will burn. So will 134a at some mixtures. You are also using it in a sealed system. Even if something like a compressor blows and caused spark you end up with a possible flash fire. Moving down the road at any speed if this happened would be no big deal. In 25 years of driving I have yet to have a compressor blow. In a wreck you may have a flash fire that would burn out in a matter of a couple of seconds. You could have this anyway since the oil used in your A/C system burns quite well when atomized into a vapor and that is what will happen if the system is broken open. I will take the colder vent temps, less strain on my A/C system, and much lower cost not to mention the 0 cfc content. It is harmless to the ozone.