Rear Spring adjuster tool

What spanner are you using to adjust the preload on the rear spring

I've been using one from my R6 but it doesn't fit too well.

My KTM dealer says there isn't a "special tool" available for this, they don't have one in the workshop even

I have two, one's just a generic C-spanner that I bought, the other is from the toolkit of my SV. They work fine... but don't bother trying without removing the shock.

The manual says nothing about preload on the rear. I've measured my spring at 178mm. Interested to know if anyone has something different and what effect it has has. For me I think it could possibly do with a little less preload so the spring length shouldbe longer.