We joke that every rack we build comes with a bicycle... and building racks is truly much harder than it looks and a good place to hone one's brazing skills (if you braze).
Built a simple rack for my wife's Peugeot designed to handle a Carradice shopper which is a rather large bag, at some point we will be refinishing the frame and will integrate the rack. It replaced the stock Peugeot rack and I wanted to retain the very simple design albeit in a much stronger and stiffer rack that would support a rather heavy single bag as well as dual panniers.
A rack I built for a friend... it had to support a child seat so seat stays were used as lowers and this was integrated into the frame before it got new powder.
We also build separate racks specifically for touring applications... the double rail lets you top load the rack and not have that interfere with the panniers opening and access.
I am starting to take over this end of the business so my partner can focus on hubs and frames and have some designs in the works.
One more... this rack came with a complimentary tandem...