Car carrier cargo coverage?

Trying to get a quote for a haul and tow type truck and i seem to be having issues with cargo coverage.
In NY, progressive is classifying the truck as a car carrier and not a car hauler and offering only on hook coverage for cargo.
To the best of my understanding car carrier is a rolloff tow truck and on hook coverage is tow truck insurance, is that correct?
I have seen a few loads that put "No on hook" in the load comments, is this common for a lot of auto transport brokerages? Trying to understand if this is an issue I will be running across a lot?

Could I insure the truck as a car carrier with progressive for liability and get regular cargo coverage through a different insurance company for auto hauling?
If the truck is being insured as a car carrier do I need a tow truck endorsement?

When I ask insurance agents these questions they seem dumbstruck and dont have a straight answer for me. Called other companies and its always something, OOIDA won't insure anything under 26001 lbs, other companies are quoting me insane prices even with a clean record and almost 2 years experience and still seem to not understand what type of truck I am talking about even after I send a picture. One of them kept saying that it is a truck tractor even though I keep correcting them that it is a straight truck with a car hauler bed and not towing anything.

This is the last step keeping me from purchasing and building the truck and getting to work. Any tips or advice?

 

Progressive won't let me put cargo insurance on this new truck I want to buy, only on hook coverage.

Don't have the truck yet, i wanna get an idea of the insurance before I do.
This is exactly what I plan to buy/build: