I found this info ....a thread is on the 1800 Trike forum below
This is a photograph of the saddlebag frame. It is just square box tubing the same size as the reciever hitch opening. One piece goes from the reciever hitch all the way to the back of the saddle bags. The other piece goes on top of this, making the saddle bags about a 1" higher and I would suspect higher for the mufflers exhaust. The uppper box tubing has a square frame attached to it which would fit where the bolts from the bottom of the saddle bags would bolt down.
It looks to me like the upper piece of tubing can be fitted by bolts to the lower tubing so that it can be moved up close to the bumper, or farther away in order to allow opening for the trunk. The frame is covered by a thin plastic piece to keep out dirt etc from the bottom. The top is covered by vinyl top that is snapped to the saddlebags and has a zipper down the middle. I thought the zipper down the middle didnt give you enought room to access the middle section.
I plan on having a local welder build one and make it long enough so that I can still open up the trunk.
I also plan on having my local uphulstry guy make the vinyl cover and put the zipper across the back end then down the side and across the bottom end, so that it would zip back making easier access to the middle section for a cooler etc.
Will let you know how it turns out.
I need two rear taillights for my project, as my originals were used in the trike conversion, so if you have two that look like a 2008 model, I am looking to buy them.