Think I’ve fettled my rear shifting too.
I cut a length of fairly rigid rod from an old golf umbrella canopy and I have taped it to the rear mech cable, from about 7cm up from the lowest cable guide on the seat stay up to about 7 cm from the bottom of the top tube. The top cable guide on the seat stay now has a loosely fastened zip tie through it. This allows the cable to move but forces it down towards the mech were it makes a nice wide loop. Seemed to work perfect last night, I just need to neaten it up a bit and post some pics.
