I have a few problems with my pickguard currently. Firstly its a Mexican P bass and at the very end of the pickguard (near the knobs) the screw has come loose which means it has a crack at that end causing trouble with the jack socket to. I thought easy to sort out with a new pickguard but found out this one has 17 holes in it so I wondered whats the best way to fill in the holes or should i not bother and just screw in the normal 13 on the new one?
i would recomend getting a new pickguard. ALL PARTS has a Fender P bass model that is very precise (i bought one and evrything lines up perfectly on mine)

if you want to keep the "wired" pickguard i would screw in the normal 13 it wont look bad haveing the extra holes not filled in. it's a good place to start anyway. i wouldent ever recomend screwing extra holes in your bass to suit the pickguard. your pickguard should have extra holes(or less) to suite your bass!
ESP B-405,Fender American Jazz Bass(EMG J active pups and LEO QUAN BADASS II ) squire P bass(EMG P active Pups)),
SansAmp Bass driver DI
Ampeg SvP PRO Tube Preamp
QSC2450 Power amp
Furman PL8
Sorry you got it confused, the pickguard already in it has 17 as it had custom parts added to it to begin with which means there will be holes under the new pickguard so i wasnt sure if it was a problem at all.