User, you said "I've found that the beavertail on my semiautomatics pounds the thumb-knuckle too much with a one handed grip" based on that I think a minor adjustment in you grip may be necessary.
You will note in the description here that the beavertail should not be inline with that area. It should be centered in the hands web as shown thus eliminating your problem and aligning the barrel with the forearm.
From Matt Temkin’s “Point Shooting Lesson Plan”
3) How to grip the pistol. Place your finger on the trigger, on the first crease, and grip it until it shakes. This is the convulsive grip as taught by Fairbairn. The handgun should now be in perfect alignment with the Y of your hand. (See pages 107 and 129 of KOGK).
Let me know if this helps User…