Sorry Jim.
When I fitted the Wonky Donky spring and guides to my 99, I didn't take any measurements.
I'm sure Bigtoe or Wonky may be able to help out, though.
Hope you're okay and still loving the Technical Airgun articles. Keep them coming!
Unfortunately, I haven't managed to put many shots through my recently acquired .177. Just a few last week to establish an approximate zero. It's doing 10.5 with 'Domes and is so very sweet straight out of the box that, unless anything were to start feeling untoward, will be left untouched, certainly in the short term. Very mild mannered, with minimal sight picture disturbance and no twang at all. Was thinking of dropping some moly paste in on the cocking link, but all seems fine.