I have been repairing guitars for over 15 years if you have a hole in your guitar doesn't matter if it's hollow or not first you do not want to de-value your instrument, depending if your guitar is maple, rosewood etc your need to purchase a simular make of wood from a timber merchants. if the hole is very deep fill three quarters of the way with resin mixed with hardener, once it starts to set plug with the piece of wood you brought and cut to size, make sure your wood sticks up by 2mm above service as resin shrinks slightly. then when dry gently rub down with wet and dry paper any gaps mix resin and hardener with saw dust from your cut piece of wood and place in gaps again allow to dry and rub down to smooth finish and paint or stain to match original colour. Hope the helps all the best Vince.
Vinciano Gallini, August 2005