so ive been running a mag mount on the trunk lid of my 4runner for about two years now, diamond SG7500A dualbander, and honestly its been fine for local stuff but i keep reading that a proper NMO through the roof is noticeably better and i'm starting to wonder if im leaving performance on the table. the mag mount does okay but i notice on the 70cm side especially things feel a little mediocre compared to what guys on my local repeater are describing with their setups.

the thing is im kind of hesitant to drill a hole in a vehicle i still owe payments on, even though i know intellectually that a good NMO mount with a grommet is basically weatherproof if done right. has anyone actually done a side by side comparison or is this more of a theoretical thing where yes the NMO is better but in practice day to day you wouldnt really tell the difference for simplex and repeater work around town.

also slightly related - does the trunk lid location actually hurt the pattern much compared to center of roof? i've seen arguments both ways

I drilled my Tacoma about four years ago and honestly I wish I'd done it sooner. The mag mount always had that slight lossy connection at the base and on 70cm you really do notice it — the band is just less forgiving of impedance weirdness. Did a quick A/B test when I switched over using a handheld as a reference and the NMO mount with a decent Larsen antenna was clearly cleaner, not night and day dramatic but consistent.

The trunk lid thing is real though. You want the antenna as close to center of the roof as you can get for an even pattern, trunk lid puts a big chunk of metal asymmetrically around the feedpoint and it shows in the radiation pattern, especially on UHF. For just hitting repeaters in town you might never care but if you're doing any simplex work or trying to hit something marginal it matters. My suggestion, find a used vehicle you like and just commit to the drill. Or if you're dead set against it at least move the mag mount to the roof center and see if that alone helps your 440 situation.

yeah the trunk lid placement is probably doing you more harm than the mag vs NMO question honestly. i ran a mag mount centered on the roof of my jeep for like a year and it worked totally fine, better than my buddy's fancy NMO on his quarter panel which is arguably even worse than trunk lid. ground plane geometry matters a lot on uhf.

that said once i finally did the NMO install i did notice the SWR was just cleaner across the band, like rock solid 1.1 on 2m and pretty good on 70 too. the mag mount was reading fine on the meter but something about a proper mount just feels more solid. if you're worried about the hole just do it at the headliner area near the dome light, thats where i ran mine, easy cable routing and you barely even see the connector from inside.