160mm vs 170mm Leitz

[Rene]

Hallo,

I have a Leitz Diavert (170mm) with trinotube with an adapter more or less similar to this one, but then of course for the 170mm system:

(this image is nicked from optik-online, thanks Herr Woitzik)

Now, I want to adapt this part so it can also use Olympus NFK (160mm) projectives. What amount should I be taking off the bottom/side?

170-160mm is of course 10mm, but if talking about eyepiece pick up point, I believe the difference is 18mm (170mm Leitz) - 10mm (Zeiss/Olympus)=8mm!

Am I forgetting something, I would hate it to discover later on I took off too much material...

Thanks, Rene.