It's your rifle (if you go ahead with purchase), but allow me to be the first to publicly cringe at the thought of modifying an original Mannlicher Schoenauer M1910, unless it's in awfully rough shape to start with.

My suggestion would be to try the rifle first with only the iron sights. The early MS rifles (I have an M1910 Takedown) were designed and configured for fast, instinctive sight acquisition (snap shooting) with iron sights. They were highly regarded, in part, for this reason.

When using a claw mount scope (mine has a period Gerard 'B'), the geometry goes cattywhompus a bit, thus I see the desire for the lowest mount possible. If it did not have a scope, however, I would not add one as original, uncut, MS rifles aren't getting any less rare and desirable.

The post - WW2 models of 1956, 1961 , etc. were better suited for scopes with their 'Monte Carlo' stocks. The later ones are predrilled for a side mount. I believe they also had an additional safety.

Again, though, most importantly... it's your rifle.