All new configuration done - which reveals a new issue...

[Simon]

Charger is now sorted, batteries are now under car, I had made a new
engine mount - lower diff and better geometry for half shafts - and
now I seem to have some mechanical issue, engine seems too loose. When
I put it in reverse or use regen (so, torque is same as reverse) the
whole drive system judders. I figure that the rubber bush mounts on
the rear part of the engine frame are too elastic.

This means I have to change two rubber bushes on engine mount to
tighten it up - that's the next move. Shouldn't be too complex - I'll
just put some wooden blocks in at first - but need to get it onto the
garage bridge to get under it.