I'm gonna throw in some observations here that I don't claim to be gospel, just humble,opinion. If the trunk,is what's swelling (vs the board), thinning the board might be a never ending process till you can't do it anymore. Rust never sleeps. Once that process is underway , I think you're boned. If you thin that board ....eventually that trunk will swell more and pinch it again. If it was me (and it has been three times now on three boats)....it's time to bite the bullet and fix the keel. You have got to find out where the water intrusion is happening, remedy that, then get that wet rusted stuff out of there. Its not gonna dry on it's own no matter how many holes you put in it. I even tried pumping compressed air into my 23s keel for a week in single digit AZ humidity. When I finally opened it up it was till a sopping wet mess inside. If you get that stuff out of there, the trunk will come back into shape, or you can use wedges to force it back while reinstalling lead and resin . If the trunk/keel is swelling and not remedied, eventually you can end up with the worse case scenario like my 17 had....where both the trunk and outside of the keel both split wide open. Thinning the board will buy you time but it won't remedy the situation, and you'll end up needing a new board as well. Of course , the statement above is worth exactly what you paid for it! Hang in there...at least you are sailing a Monty, a boat well worth the effort to repair! :-) S Sent from my Verizon 4G LTE Smartphone