The tallest loads I've been on we're about 13'8" required a overweight permit but no big deal, usually the foam insulation or hay and hay sucks pays diddly squat and if its for horses has to be tarted. It's not that bad really most places require you to tie off meaning you put on a harness and clip it to a cable run, I'm not thrilled about heights either but it's cake. They put the tarps on for you so you don't have to carry them up a ladder or anything. Don't worry when you go out with a trainer ask him to try to get a load from Owens Corning or johns mannsville. That's the two main places we get that from( foam insulation). Also ask about rolled roofing that can be tricky and is a high load as well.
I will say that you all have some beautiful Peterbilts, that is what first got my attention with TMC.
Rode with hubby six weeks, January and half of February. Rider insurance was 5.00 a week 2 1/2 years ago. Your wife will need her birth certificate, marriage license and drivers license all copied and mailed or faxed in. We did it all by fax. Very painless. You do need to be prepared though some companies will not allow her to be on their premises. I had to spend couple of hours at a Pilot while he picked up load. Some will let her on premises but not allowed out of truck. Just make sure your dispatcher knows she is aboard and they are good at telling you what she needs to do.
