I called one place and was told for $50 for a half an hour time, he'd go up on the roof and move the dish around till the strengths were better. I believed he mentioned the birddog was around $700 and he didn't want to pay that much. I haven't called anyone else since I haven't had any problems with drop outs.
That's why I was questioning if you really need 90's, when mid 80's and some 70's on a clear day seems to work for me. Even in the pouring hard rain when my sigs go down to high 30's, nothing seemed effected. I can't imagine a harder rain then when that happened. Super foggy nights will get me down to the mid 60's on some, again, with no drop outs.
Just from my experience in southern CA, mid 70's and 80's on a clear day don't seem so bad. The OP was saying he was getting drop outs in the mid 70's when I don't get that on the high 30's in a rain storm, so maybe it's something else going on for him?
You are obviously an experienced person with dishes, and I highly doubt most people get 90's/high 80's across the board like you. I really don't think it's needed to be that high to be problem free. And I hope I didn't just jinx myself by saying that.