Cut them in half and deburr. Then make a cheater handle out of some tube. Flatten the end of the tube slightly until it slips over the wrench shank. That gives you a short handle wrench to manipulate the jam nuts until they start needing more force and you don't need to swing a long handle around. When they start getting tight, slip the handle on and get after it. Also much easier to line the wrench up on the flats and then stick the handle on.
I give mine everything I've got on a 24" breaker bar. I'm not sure a 3/8" would stand up to that, but it'll probably be ok with whatever length it comes in as long as you don't put a cheater pipe on it.
Edit: forget everything I've said on this thread, pretty sure Blaine's advice is about to change my life.
I use one of these for my jam nut. Doesn’t seem to expand like a regular adjustable wrench. Make sure the force is on the fixed jaw. A pipe will slip over the end easily. https://www.amazon.com/dp/B000TDGHF0/?tag=wranglerorg-20