I am, alas, far from that rifle. You may be best off phoning Mr. LeBas, that seemed to work better, at least to get started.

His technique is based on his "hobby" of collecting scopes and mounts. He will then file to fit your mount.

My M1910 also needs a mount. I am planning a trip to Vienna (actually closer than my M1903 right now), and I will be stopping in at Johann Springer.

Only other option I can give you for measurements is to find every photo you can on the web, and go from there. At some point, the proportions will make sense.