newbie stereo install question
 

bought the Clarion CMD6 to upgrade from my XMD3 for my '02 SAN. the hole is just a little bit too small and the new unit bumps against the top lip of the opening. What's the best way to slightly widen the opening for the new unit? Is it just to get a mini hacksaw and carefully cut it a little wider (top to bottom)?

Dumb question i know, but this is definitely not my area of expertise...