Howdy! 

You can remove the band, and carefully sand/file between the halves of the screw lugs to allow it to clamp a little tighter on the stock.

As for the peep, CMP allows you to enlarge the peep to 0.1.  On the 1901 sight, there is enough metal to support this, however on the Sgt. Peep plate on the 1902, I found that 0.07 was about as large as I dared going without damaging the plate... and that was sufficient to make a world of difference in sight picture.  On that 1901 sight, I would go slow and careful.  Shouldn't be a problem.  DO NOT exceed the 0.01 diameter allowed.  If you shoot for a medal at Perry, they WILL inspect your rifle, and if you are larger, they will disqualify you!  Use wire gauge drills, and I recommend carbide if you can find them (Sears should have these)