If you go with a 1x pin, all you are doing is tightening the tollerances. obviously, tc already provided you with a oversized hole. they do this for ease of barrel changeabilty. i would think if tightening tolerances has an adverse effect on accuracy, then there must be some real issues with the particular frame/barrel combination. It may or may not effect accuracy, but i like a tight lockup.
As far as your reloads, if you haven't already tried this. I take my best powder/ bullet combination and then i play with the the seating depth of the bullet. sometimes this has made a so so load into a shooter with my tc's.
also, if you don't already do this, when shooting from the bench, try positioning your front rest very close to the frame.
everbodies accuracy standards are different, i.e. one inch or larger is fine for deer, but is marginal for prairie dogs.