3/4 is huge. How many more crew did you have hike? I don't think you'll see more than 1/4 per side. Note there is a spec on keel weight. Truing the keel might remove enough weight to violate the low limit (not that anyone would know without weighing). But, I would be concerned with such a small, low aspect ratio keel that the loss of weight (higher metacenter, less stiff boat) offsets gains in speed (from reduction in Cd, Cl coefficients) a thinner section would provide. You can always build it back up, but not add weight (new keel). Lastly, if you thin the section, watch the stub the keel plugs into (don't cut into it). I think the stub is fat too, and would require some transition fairing to a thinner keel. A little simulation would answer the trade-off questions.
