mine is on the roof.I put it up 2 weeks ago in place of my really old 18 in single lnb. I used a 12"x12" 1/4" thick aluminum plate under the dish mount to distribute pressure over the shingles better to keep the dish mount from crushing through them when tightened down and put roof/flashing sealant around the lower side to seal it.I positioned it with the centerline screws right into a roof joist.For the outer sets of holes I cut 2 2x4's about 3' long,drilled through the roof and placed the 2x4's inside the attic and screwed through the outside holes into the 2x4's,the extra 2x4 length gives it a lot of support.Then obviously make sure its all sealed good.My old 18" was mounted the same way in the same spot for at least 12 years with no issues,the at9 has been up for a couple weeks now with no issues.It takes 2 people to do it this way,grab a buddy and shove him in the attic.I agree with charper1,installer just doesn't want to put forth the effort or more than likely doesn't want to be responsible for a leak if he doesn't get it sealed properly.
