This is the first bike I am building. The base is a BMW r100 (1983) which I am trying to turn into a cafe racer. I have decided on using slanted shocks (I know I will be sacrificing some handling for the aesthetics of slanted shocks). These usually go well with a solo seat, but I was kind of hoping to take a passenger sometimes (not for long distances). What would be the MINIMUM seat length I could get to have a ride passenger (they don’t have to fit comfortably because it is only occasional and for short distances).