Installing new tuners

i have a used, via eBay, mod 12W McSpadden which has a scroll head with friction tuner pegs using 1/4” peg holes.  I would like to replace the friction pegs(make unknown) with Grover geared tuner pegs which  require 5/16” holes.  Are there any “gotchas” I need to know before I start to drill out the holes to 5/16”?  This dulcimer sounds great and I would like to keep it that way.  I do have reasonable woodworking skills.

i posted this discussion elsewhere on the site, but I now think this location is more suitable.