Whelp, after about two months of re-work.. i have completed fixing everything i screwed up with the wing attach. Here is what i did:
First off.. i convinced myself to rebuild the entire spar box, all four wing attach brackets, and the aft shear plates. I figured there would be no way that i would be able to drill out and match drill all of those countersunk rivets, and that i would be much happier with myself if i just re-did the whole thing. This also meant re-making those brackets that come off the aft of the spar box through which the flight control stick assembly mounts to.
I then re-made all of the bearing blocks for the main wing spars. Twice, actually, because i wasn't happy with the way the first re-makes came out. I first tried to make just the bearing blocks and match drill the existing holes into them, but with less then acceptable results.
For try #3, i just remade brand new bearing blocks and bearing block angles, which required drilling out four solid rivets in the spars. One of them got wallered pretty bad, so i up-sized it to a -6 rivet. I then jigged up the wings on some saw horses with only the blocks/angles on the forward spar and set up a drill bushing guide on the aft spar. I grabbed the location by putting a 3/8" bearing into the guide, using a 3/8'' rod inserted through the bushing and into the existing 3/8" (ever so slightly wallerd) hole in the two spars.
I then used my fancy 3/8" with 1/4" pilot bit to start a 1/4" hole in the forward side block/angle, then changed the 3/8" bearing to a 1/4" bearing and punched through all the way with a 1/4" hole.
Then i took the wings apart, installed the aft blocks/angles, re-jigged the wings back together and transferred the 1/4" hole through the aft blocks/angles using the now existing 1/4" hole in the forward ones as a guide. This process, although tedious, left me with perfectly centered 1/4" holes to the existing holes in the shear web of my wing spars.
I then re-jigged the wings to the fuselage and repeated the whole wing attachment procedure for a second time, however this time i used the fancy 3/8" with 1/4" pilot drill bit.. with the 1/4" pilot section significantly dulled out.
I was thrilled with the results, perfect holes with no slop whatsoever!!
Although extremely tedious and de-motivating at the time.. it feels pretty good to be done with it all and have an
airplane sitting there in my hangar now :D