Batboard

Will I really notice that much of a difference if I drill a hole in my trunk compared to using a trunk lip mount?

Yes. much better ground plane. Less electrical interference noise because the mount is physically grounded to the body, not 2 small screws.

Yep. Man up and drill a hole. Really, it doesn't hurt your resale value (I traded in a truck a while back with 12 holes in the roof - they didn't care) and it makes a difference in performance - especially on lower frequencies like VHF.

Oh, and center of the roof is better than the trunk... less noticeable, too.

And, not to beat the subject to death, but if you can gain access to the underside of the roof or trunk you're using then use a Greenlee 3/4 inch hole punch. Nice, clean hole with no burrs, and you'll have complete control of the process as it proceeds, with no drill jumping around in your hands possibly messing up the paint topside once you get the 3/8 inch pilot hole drilled.

This will be going on a 2004 Chevrolet Monte Carlo SS trunk is open in the center

Can I get one of those antenex hole cutting saw bit and will do the trick?

Yeah, and if you start from the bottom side of the trunk its less noticeable if you screw up. Just drill the pilot from below and then finish from the top.

Chassis punches rule..... use the smallest drill just to get the punch through then off you go..
good luck and tom i dont think that you are beating it to death... more people should use them... makes for a cleaner job... yes yes i know that if you are in a shop you need to get out many vehicles a day to keep your boss happy..