I finally decided how to attach the rear brake cable.
As the footpegs are made for a brakecable and the original S90 brakeplate is meant for a brakerod, there was a problem.
I didn't want to weld anything to the brakeplate, but I couldn't decide on what it should be, untill last weekend, when I made this bracket.
I know similar brackets exist from aftermarket suppliers, and yamaha used something like this on their 125 production racer back in the days.
It is bolted with the brakestay and has a lip that falls against the edge of the brakeplate, very simple but effective.