Let me ammend my comments above: I calculated some scenarios for leeway and boatspeed resulting from balance of sail and keel forces, upwind, due to a change of 1% in keel section thickness (nominal conditions, all else being equal). There is the theoretical potential, by bringing the section thickness down to spec, of a couple tenths increase in boatspeed, and about 1 degree less leeway. I used old NACA airfoil properties, which are pretty close to the J/30 keel profile. Curious thing about those curves, they show narrower sections reduce drag coefficient (Cd) by >5% per 1% change in 1/2-section thickness, whereas lift coefficient (Cl) is almost unchanged. That leads to a bigger performance benefit than I thought because as boatspeed increases to balance the lower keel drag, leeway (a.k.a. keel angle of attack) decreases to rebalance keel v. sail lift. (If Cl decreased with Cd, then leeway would have to increase and vmg improvement, if any, would not be as good.) Also, affect on heel is much smaller than I would have guessed (< 2 degrees). Numbers seem to support your experience with Catalina. Sounds like a win-win. Disclaimer - do your own math - and what you do with a power planer is your responsibility!
