I think you can fill that cavity with wood filler or something. flood would know more precisely.
And look for Bare knuckle pickups if you want high end stuff...
and Lundgren pickups if you want GOD level stuff xD
Classical and jazz lover. Fingerstyle, touchstyle, and ERG enthusiast.
Buying a guitar/amp/pedal/processor, and need help? READ THE GUIDE -> http://www.indianguitartabs.com/showthread.php?p=417766#post417766
My Guitar Pro transcriptions (tabs) site for all kinds of music, all genres. - http://insecurity-transcriptions.tumblr.com/
My music recordings - http://www.gimmesound.com/insecurity/