I goofed: I predrilled the 1/4" hole in the fuselage bracket and then tried match drilling into the tank bracket with less than optimum results.
What I SHOULD have done is do a careful measure of both brackets overlaid and then drilled from the front - tank bracket into the fuse bracket.
However. I rechecked all my dimensions, and had I done the latter, I would have found that when mounted to the tank and the fuselage, the brackets do not overlay nicely like the picture on the plans. I would / will reshape the fuselage bracket to put the center of the radius in line with the center of the radius on the tank bracket - about 1/4" lower. I'm just hoping I don't need to redo the tank because of the too high hole.