I think that just warming the skin with a handheld hair drier may accomplish the same as wetting it and letting it dry to whatever the humidity level is where you live

Hide generally retains most of its elasticity through wetting, stretching, and drying. If your "mountain banjo" is made the way I've seen them (hide tacked to the back of the front ring, and stretched over thin sheet metal (stovepipe or tin can), I'd worry some about that sharp metal edge cutting into the head and making it prone to tearing there when it gets re-stretched, but if that's not a problem on yours, I don't see why you couldn't detach and reinstall that head to tighten it.

How old is she?
What species donated it?
40% urea cream is available at Walgreens, CVS, etc. it’s Bovine, I think.

I suggest re-treating her with 40% which is animal-based, then after you have rubbed it in, notice how good your hands feel, since they are well………skin

Then, use a fine mist from a spray bottle and then carefully re-install the old head whose pores will stretch naturally if you go patiently since nothing is ripped. Then after it tightens up overnight, use a hair dryer without heat to slightly de-humidify, it’s ionized air.

I think this is a logical progression of events.

I subscribe and endorse a small group of people who seek a drum/banjo head made from rice paper and bamboo fibers. If the Incas can build a durable bridge out of simple grass fibers, then a paper head infused with a naturally occurring resin with pores should be capable of similar durability, resonance and snap.

I have built two banjos for people who spec’d Birch plywood @ 1/8” thick to lay flush inside a 1/8” deep ledge with small 3/32” pegs around the rim
(18 ea .) so they stay flat held by the bridge, so they could vibrate. It works and suits many front porchers from days of yore. I’ll do it again if needed.
Thanks for the opportunity.

Hey Darryl. Why can´t you just tighten the head a little. (don´t know so much about mountain banjos). Steen