2 questions

I wanted to install a component system in my front doors but it appears I'm pretty limited in size according to the book. Is 4x6 the largest size I can go without cutting?

Second question,the last 3 Caprices of mine,'96,'96 9C1 and a '94 L99 have all had static from the AM band. Even the stations that come in strong have always had a little bit of static. None of my other vehicles have static in the same areas as the Caprice,even my $59 deck/speakers from JC Whitney in my '86 K5 is clear. I'm going to install a system and I'd like to know if anybody else has experienced this and how do I get rid of it? There are times where only AM is available because the mountains block the FM signals not far out of town.