I'll try to quantify what these brackets do. Tilting the trunk 4.5 deg. up at the rear, brings the top of the backrest (assuming 12" high) about 1-1/4" forward. There is a sliding bracket to which the trunk attaches, that in its rear-most position is about 1-1/8" forward from the stock position.
The sliding bracket offers about 1-1/4" of additional movment to the front. So, the brackets will mount the trunk forward between 2-3/8" to 3-5/8". These are approximations since I don't have a trunk to measure. The object was to make the backrest more vertical and move it forward for passenger comfort, while at the same time correct an appearance issue with the ribs in the Corbin trunk not being parallel with the ribs in the saddle-bags.
Phil, I think you and CDR did quite well. I can't help but think Corbin's original intent may have been to make the lines parallel, but somehow missed the boat in the production process.