Bad idea
Mike,
Yes, these are structurally critical parts. But there's no reason to believe that these parts are a weak point in the airframe. And in any case, there's no reason to believe that not tapering them as shown on the plans would add strength in any meaningful way that would benefit overall structural integrity.
You've stumbled on a common pitfall that you should learn to avoid. Beware, in general, that going down that path -- arbitrarily adding material to "strengthen" arbitrary parts -- will lead to an unnecessarily heavy airplane that is no "stronger" than stock. And in some cases (though not likely this case) can even have more serious unintended effects, like making a structure too rigid and thereby transferring loads to other structures that weren't meant to carry those loads, etc., thereby actually compromising the structural integrity of the airframe. Anyhow, bottom line, just not a good idea in general.
-Roee