NMO hole mount in Suburban / Denail XL

[lemish]

I have a 2003 GMC Yukon Denali XL (Suburban) and have cut an 3/4 hole for NMO mount just above the farthest rear courtesey light (about 6 inches from the rear door of the vehilce.)

I want to add another antenna close to the next furthest back courtesy lamp. This second lamp is about 6 inches behind the second row seating.
I thought this area of the roof was also single layer sheet metal and can use a standard NMO mount (not a thick mount.) However another post I read here on RR has implied otherwise.

Anyone here can confirm I am dealing with single layer sheet metal near this second courtesey light?

Thanks in advance,

ML

[ResQguy]

I put antennas over all three dome lights with no problems. If you are concerned, drop the light and verify from beneath. You can flex the roof with your finger.

[lemish]

Done!