Is there also a weight issue related to the total load+car weight and driving licences ? By the time you add car+battery+load attached I would imagine it would exceed your normal drivers licence if the load was heavy? I thought I read that larger caravans plus large cars exceeded a normal licence in some cases?
I do also wonder about re-gen with a big load on it. It is going to confuse the re-gen system as the back pressure of the increased load when you lift off must peak the energy being recovered above normal levels? The computer must be programmed with a certain range of regen (light/heavy loaded car) but adding 1.2t would be interesting to understand.