OK - finishing end of page 2 on this thing. Go for OE all around is what I'd do. Why - it's all tougher stuff - an opinion. DO NOT BUY INTO THE VARIABLE TYPE. Never used but hear nothing but troubles or noise?
Now you say it's a camper back to the thing so nothing about the OE A/C would have ever cooled it as you just said.
This puts a new spin on it. Whatever if anything separate front passengers from the rear could or should be isolated as is practical and to your liking.
Haven't priced assorted refrigerants in a while but duly noted prices drop off season you may have noticed.
Going forward: Quit it with the 12oz cans and get the 30lb bottle and a scale. Fine to use the little cans but the games of changing one to the next for full charges is room to get air into system and there's enough trouble fussing with equipment already.
Nothing about A/C is particularly cheap to do right, doing things well the first time always best.
A reason to give up R-12, little cans now is ones you see for sale are old. The gas doesn't care, the cans do. That sealed top you can find them empty already untouched or rusted bottoms. The turn and pierce taps are pulling the tops such that they leak quickly for me now down to just a few more left all given to me by shops, stores, folks who can't find a use for them. Still have a new virgin Dupont Freon by brand name sealed and will crap if the stem leaks if opened.
Why new old stock? I was given a 1/2 full recycled bottle of R-12 to finish up with boosting assorted vehicles now empty buy ages ago and only boosts for mostly vehicles on their last legs totally never mind A/C. I swear the stuff was mixed or not pure R-12 product just with observations of performance a little goofy using that vs just one car left still R-12 in use by me as a real Sunday type driver or fair weather only if at all possible.
I'll convert that one if a leak shows up and need to open it up. Can't guess when or if a new leak may happen. Said in here that one is all OE untouched but did show a new car warranty job of replacing "O" rings when new. Otherwise just boosts mostly to save the compressor - already beat on that, that running system when low is the compressor killer.
I keep a wired thermos in center vent all the time on all my vehicles to watch the temp. Anytime any of them don't behave shut them off immediately and find out why right away before the grenade compressors. Done this since forever and never replace compressors in my own - of countless vehicles over the years.
Granted didn't keep many all that long mostly acquired as good fixer uppers for resale - whole vehicles - mechanic to all but finish body work.
Seems the time is coming for me to write the whole novel on how to tweak out a system and charge one that has an unknown capacity which I'm very good at. Boats (yachts - non engine driven compressors at all) , cars - whatever creation came along.
Just finding the right charge with total unknowns or boosting now older stuff takes hours to pin down just right always best when I can catch just the right day or better two in a row with similar conditions. Can heat shop to 100F is about it and done doing that for Winter is still too much guessing so put all those off in state of positive charge, system disabled till weather cooperates later.
Same problems when way too hot as well. First problem is I can't take that much heat meaning the over 100F stuff with running engines - it's all over for any car work.
Lastly on refrigerants - stay with known product, new virgin stuff, no additives, no sealers, no special oil crap just pure products.
Read containers and know it's the real stuff. All make claims of being the better product but should really be just the product no tricks or mixes - there's just no magic out there at all that makes a system better than what car makers use OE. If there was a trick product it would be used when vehicles were new - case closed on that,