Kickstand update:
The SMGT died of metal fatigue. I bought a Shiny! New! SMGTe to replace it, transferring various Perfectly Good Components over from the old bike to save costs. Among them were the low-rider rack, which had been replaced in about 2016 or so, and the above ESGE kickstand.
The kickstand got the wire brush and Hammerite treatment, on account of being structurally sound but a bit tatty looking. I also replaced the customised large-diameter ferrule
[1] with a new customised ferrule
[2], for similar reasons.
Anyway, when I installed them on the new bike, I discovered that the stand would hold the bike almost exactly vertical, to the point where a light breeze or wobbly floorboard would tip it over to its right. This improved slightly when I swapped the Boring! New! wheel (HPVelotechnik branded disc-specific rim with 40-406 Marathon Racer) with the old dynamo hub wheel (Sun CR18 rim with 40-406 Marathon Greenguard).
From which I conclude that:
a) The SMGTe geometry is slightly different from the SMGT with regard to the height of the low-rider rack above the ground.
b) Wheel/tyre dimensions make a difference to optimal kickstand length. (With hindsight this is obvious, but it's easily overlooked.)
After a couple of iterations, I've hacked about 10mm off the kickstand and re-moulded the ferrule, achieving a lean angle that's stable but slightly more vertical than the old bike. I may come back and shorten it a bit more, if necessary. Hard to find the sweet spot when you can only adjust it with a hacksaw.
[1] Mild steel L-bracket and Sugru.
[2] Stainless steel penny washer and Polymorph.