OK. I finally received a package - the day BEFORE we put the MH away for the winter!:R It was the baseplate brackets. The adapter plate is STILL on backorder. It's been 12 WEEKS already! When this entire episode started, they gave me an approximate lead time of 2-1/2 to 3 weeks.
Roadmaster-tow-bars.com (Not ROADMASTER INC. the manufacturer) is a joke! Stay away from these clowns! They also go under the names of prohitches.com and hitchfinders.com. Probably a couple of others too for all I know.
Now we'll see how long it takes to get the backordered item.