Humidity is key when drying larger diameter items. If its too dry, the surface will dry too quickly and lock in the internal moisture, possibly leading to spoilage. If its too humid, you'll get lots of nasty mold and the meat can spoil before it starts to dry out.
Meats with thinner cross sections, like jowls, duck breasts, unrolled belly, tri tips, pork tender loins (which happen to be all things I've successfully dried at 55* 55% RH) do ok with less humidity.
If you conditions are similar to mine with low humidity, you can try doing what I do. I alternate the meat from hanging to bagged in a fridge. The time in the fridge allows the moisture inside to redistribute itself. But if this is your first try, then I wouldn't over think things too much. Cure it, hang it until you've lost 30-40% of your initial weight, cut it and if it still seems too soft/raw in the middle, bag it in the fridge and forget about it for a month and it will be perfect. Additionally, guanciale is typically cooked, so it can be hung for as little time as you'd like, just store in the freezer similar to bacon.
here's a link to some deer that I cured, you can clearly see how it cures unevenly when conditions are too dry (but not dry enough not to try
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venison bresaola