yup, hit the nail on the head. I think few sales guys understand WD hitches and the installers if the do aren't the ones that interface with the customer unfortunetly.
John all the folks I helped had very little knowledge of how a WD system works and the dealer did a WD setup with an empty trailer. Unlike them, I had some knowledge of WD setup and redid mine once I loaded up. And I happened to hit this forum with info from you and others on setting up WD properly.
And like you mention GM front bump stops only have 1/2" of clearance or less, so don't try to drop below unloaded height.
And for hookup I've had a few people who tried to hook up with the TV trailer combo in a "V", when in a sloped driveway to the street and they don't realize that the "V" adds a great deal of load to those bars, can be dangerous unhooking if not careful or very hard to hook up even by using the jack to lift the tongue. Once I gave them a physics lesson they had an "ah ha" moment and they realized they just need to pull the trailer out of the driveway and get flat in the street then hook up the bars.