What PACNWDude said:
Nice to see someone with NMO mounts in the roof to be honest. My employer is getting scared of this, but then I have a fellow co-worker that needs more training on NMO hole drilling (also need some new bits that corporate says are "too expensive") ...
First...construct your own hole saw.
Laird 3/4" diameter hole saws are price $75-$95, one outlet for $165.
Walmart set of 4 for $8.
Harbor Freight and Northern Tool set of 8 for $5.
However the 3/16" dia arbor bit is longer than the metal roof and inside roof liner space. If the arbor depth isn't adjustable here's a solution:
Take a 3/16" drill bit, tape strip of tape 1/4'" from tip, drill hole to depth of tape. This is your pilot hole.
Take 3/16" bolt longer that arbor bit, cut off threaded end, insert threadless bolt (cut to to length such that bolt extends only 1/4'" beyond hole saw blade), insert bolt into hole saw arbor.
Wrap tape around hole saw 1/4" from cutting blade.
Now you have a hole saw with arbor center bit that won't reach roof liner.
Drill hole 1/4" deep using threadless bolt as centering guide.
Gather your new tool and keep in plastic bag for next antenna mount hole.
Next plan you antenna placements, with expectation you'll want to add more antennas. [Guilty]
First separate antennas by wavelength used by 3/8 wavelength. My 2m whips have 28" separation from other antennas, my 70 cm antennas use 10"
Second for adequate ground planes, at least quarter wavelength from sides of roof, and front and rear of roof.
From the sides, and front and rear for 2m that's 19"; and for 70 cm that's 10"
I try not to look like a whacker at least.
Guilty
with the complete set of antennas attached, a young gent at a service (let's just say 'gas' station) said 'What's all that stuff for? You talkin to aliens or something?'
Gas station attendant asked if I was some sort of NASA rescue team.