Anyone done this? However i configure the two seat stay mounting arms i cannot get it to fit. Am i missing something?

If i put them on as in the instructions the two bars touch because the wishbone is narrower that a normal a stayed frame. I could put spacer in to keep them apart but I am then concerned that the load in on the spacers as this is to mount a child seat on so would prefer them to mount solidly to the frame.

Swapped them side to side and that doesn't work as they then stick up too much to get the seat oon.

I am loathe to start bending things on a new £100 purchase and really don't want to take it back as it is a nice seat…

any advice greatly received form the STW massive…