Just my experience. Today's cars seem to have a lighter sheet metal
thickness than days of yore.
I used a Greenlee punch on my 91 T-Bird.
Curses - put a dimple in the roof.
Forget the hole saw -- dimples as well with too much pressure.

I Asked around and the gurus say to use a Motorola tool for this -- outfits
that do police, fire installations etc will have these.

Be sure to seal the opening after installing the roof mount -- the same
outfit can advise. I found the o-ring to be not good enough

I like the roof mounts -- makes a good connection with the car metal.

And you can swap whips easily -- for 2M I use a 1/4 wave around town and a
5/8 for trips.

Really haven't found much 440 activity while traveling, so I use a 2M 5/8
wave and watch the clearance in parking garages - hi hi.


Haven't seen a comparison of mag to roof hole mount performance - but mag
mounts worked OK on a rental car I got for a trip back east

Good Luck

--
Incognito By Necessity (:-(

If you can't convince them, confuse them.
- - -Harry S Truman




wrote in message
...

I used to drill holes in my new rides. Isn't a good NMO mag mount just
as good performance wise? I want to use a 43 inch dualband (144/440 mhz)
antenna.
I get nervous in my old age punching holes in the roof of a mega$$$
truck.

BTW: Repeaters in far West Texas and Southern New Mexico are on top of
high mountains. 1500 to 9,000 feet above average terrain.