Mounting NMO antenna to aluminum truck cab?

[JohnDeere7920]

Hey everyone. Had a quick question about using one of the dreaded magnetic hockey puck NMO mounts in my 17 F350 which is of course aluminum. Obviously magnet won’t stick to the top of the cab so I’ve put some felt down with double sided tape to stick it there for my ground plane. 
 

question is the felt and double sided tape interfering with good grounding of the antenna? I really don’t want to screw anything through the top of my cab to secure the antenna mount to. Right now radios work in excess of 5 miles but if somehow fixing this would get me some more miles that would be great. I don’t have an SWR meter to check any of the specifics. Just bought MXT500 radios for farm use so communicate is kinda important at times. 
 

what’s everyone done to remedy the aluminum cab issue? Thanks I’m new here btw so bear with me as I learn these things. We’ve had business band radios for years but they have stopped working and now going another direction since we can’t fix and program our own radios. 
 

WSJV395

[RoadApple]

4 hours ago, OffRoaderX said:

WARNING!!! "some people" are going to try and convince you that your setup will not work, nobody will hear you and it will burn-up your radio, because you do not have 6 inches of metal/ground plane in all directions under the bottom of the antenna..

As you probably already know by your real-world experience of actually using your setup, they can be ignored..  "some people" have difficulty differentiating from "the best" or "perfect" that they read about in a book and "plenty good enough for normal people outside in the real-world".

 

Yeah, you are exactly right!  I heard that proclamation/warning and chose to ignore it.  I'm not a radio purist so as long as it works reasonably well, I don't really concern myself with all the technical perfection (usually only detectable with test equipment).  The photo I posted above shows the 3rd brake light mount with a dual band 2m/70cm antenna, but most of the time I use a little 6" Tram 1126-B 1/4wave antenna.  I like that little Tram because it is very low profile, and most folks do not even notice that I have an antenna up there.  My SWR is 1.2:1 on my Btech 20W mobile and it works great for my real-world purposes on both GMRS and 70cm. 

In fact, based on my experience, I might argue that for UHF, ground plane is often over-rated.  I can drive in circles, presumably transitioning between lots of ground plane (to the front) and arguably zero ground plane (to the rear) and the folks I'm talking to usually can't tell the difference.   That's good enough for me!