I do not own a DP, but I have been shopping and the cargo bay dimensions are important to me.
I want to carry 2 mountain bikes inside the cargo bay.
The width generally runs from 36 to 46 inches.
The height measured from the top of the sliding tray to the bottom of center rail runs from 13.5 to 18 on the rigs I have measured. If you remove the sliding tray, you can get 2 more inches.
I have been shopping 2005-2009 models. I think the newer chassis have a bit more height.
I have decided to slightly disassemble my bikes to get them to fit. If I remove the pedals and detach the handle bars, I can fit the bikes into a 10 inch space.
I will probably build a lightweight box (sheet metal) to contain the bikes so they do not move or bounce around while travelling.