Costco has a temp probe set which includes a 4" ss probe. It's digital and wireless. Is there a practical way to fit this into the wall of rubbermaid round coolers?
might just be better off pushing it down ito the mash and pushing the lid down over the wire.
I know some people have had issues with moisture gettting in the probe of some digital thermometers (wireless and remote read). Baking it usually fixes it.
I don't see permanently affixing it being a good idea. Other than interfering with mixing the mash, variances in the mash temps makes it not worth the trouble.
I've tried both the dangle in mash and permanently installed probe techniques in my keg MLT. I have much preferred the permanently installed setup. No matter what, you're only getting a reading from a single point in the mash. Worrying about getting the probe braid wet is a major PITA if yours doesn't have a silicon shield (which is another option).