My own bike, POP, has evolved into the golden, single seat version below.
I am in the middle of building a second bike for myself that will be used for 2-up duties and touring. I had to source and build another engine as the donor bike had a grenaded engine. I upgraded wheels and brakes at the same time. I just got the engine back in the frame last weekend but there is so much still to do and not enough free time so it will be a slow project.