So a bit of an update.

Using the parallel tub and straight edge of the rear wheel and some school boy trig I found OSR had 1 deg toe in and the NSR (in the photo!!) had zero!

So a bit of a fiddle on the nice adjustable trailing arms I got c0.4 degree toe in one both rear wheels.

Set the tyre pressure to 18 front 22 rear ground clearance front of tub (which is essentially a flat plate) 160mm, rear of tub 169mm so not pointing up!

Went for my 20 mile check run and the rear felt really planted, but am still not getting a stable front end at speed in a straight line. Steering and cornering so far feel fine but not exploring that. It needs constant input on the steering at ehem speeds in a straight line (like it is tram-lining all the time), not as bad as previously, so more toe in or less, and more caster (I am near the limit of the geometry already at around 5 degrees). I did not notice any bump steer problems.

Any chassis experts out there??