I love the DIY part of this hobby. 2M from the couch was stale and CB held no interest for me. So 2M/70cm mobile. (on a different car, to eventually include 10 and 20m). I started out with the least compromise possible for 2/70. That meant center roof mount. I once had a magnet mount antenna for CB, back when I didn't know any better. Now that I do know better I went with the NMO mount and of course staying in Amateur Radio. My apprehension was the same as anyone else; "Drill into my car!?!??" Once I finally did buy the parts and tools it still took me 5 weeks to build up the courage. "Do I really want to do this?" lol Then I just said the heck with it. I messed with the interior trim a bit to see if I could avoid dropping the headliner. It was possible but I would be more comfortable dropping at least the aft section. So another three weeks after that I finally decided, again lol, the heck with it. So with cloudy skies I pulled out the C-pillar trims pieces, the rubber seals on the doors, and the B-pillar trims to drop the aft portion of the headliner. Earlier on I had criss-crossed some paracord on the roof to give me the center point but it was a bit far back. So this time I just took a cloth tape measure offset back a little from the cross-member, and marked off the center. Took the inexpensive Harbor Freight 3/4in step drill bit and went for it ............ I put a dab of Nyogel on the o-ring of the NMO mount and gently snaked it into position from the outside inward, being extremely careful to keep that outer ring connected to the inner portion of the NMO mount, otherwise it would drop into the car and I would have to start over again lol. I then put a dab of Nyogel on the o-ring for the antenna and snugged that down tight as well. At that moment it began raining. I swiftly, yet smoothly, ran the rubber seals back into place and closed up the car. Trim and headliner would have to wait lol. But once that was over I buttoned everything up, discovered no leaks, and we were good to go. SWR is 1.0 at 139.4x and 1.5 at 146.5x. I'll just leave it. Here in the flatlands of south Florida I'm able to kerchunk the repeater 40 odd miles away but unable to copy a response. That's using my Icom V8000 VHF gobox at the 75w setting and sitting on the passenger seat. Another set up is the HT with a pigtail and hand mic. Less reception on the fringes and simplex but perfectly usable as well off the repeaters. That center mount really takes advantage of the resulting ground plane.