Nice work. Your B pillar still looks to be in great shape. Yes, I would use the copper backer. I found that even cutting back the old metal to the good stuff it still has an easier tendency to blow thru. Cut a length of wood to hold it up tight to the bottom side from the floor if the magnets don't want to cooperate.
I got good penetration to the backside. Probably because I turned up the wire speed some since I blew through in a few spots. Once I sped up the wire that problem went away. But, as you can see a little more metal to grind.
Did some more cutting this morning. This side went much smoother than the other. Maybe I am getting better at this. Hope to finish up by tomorrow on these patches and on to the driver floor pan. My air hose coupler sprung a massive leak so it is break time and off to Lowes.
Well, realistically I probably won't be ready to send it off to the media blaster until November. And that is my problem now. I want to spray the bottom with epoxy primer and Gravitex and I am afraid it will be too cold by then. And I don't want it to sit bare metal all winter so I may opt to hold off until late March. I can use the winter to finalize and power coat all the accessories, etc. I am not going to paint the whole thing in my garage. Just the bottom and inside so I can seam seal and take it to a painter.
Paul, 2 1500 watt heaters can work wonders for taking the chill out of a garage. I buy 2 cheap heaters ($21each. ) every year, and get the 1 year warranty, in the spring I take them back because they stopped working) Menards, lowes, Home Depot) they run pretty much 24/7. 3 to $4 bucks a day to operate. It's just enough to keep me working.
And practice makes perfect!
1957 WILLYS pickup,
1973 J 4000,
1978 CJ7 DD.
1979 CJ7 360, TH400/Quadratrac.
1980 CJ5 trail Jeep.
1989 YJ the CJ to YJ.