So I had a look at the rear base and the factory unit cannot be used as it is, as the mounting tabs have two holes which are counterbored to take cheesehead screws. The thickness of the tab is such that when counterbored to the depth of the head, the amount of material remaining at the bottom of the tab is only fairly thin. If you were to machine a radius at the back of the original base then all the material at the bottom of the tab would disappear and the screw head would fall through.
The only way would be to make a new rear base with thicker tabs or instead using countersunk screws to allow for the radius at the back of the base. One could use all the remaining parts from the original base.

Interestingly a Kahles Helia S2 2.3-7x32 is exactly the correct length for such a set-up giving the correct eye relief and objective bell position.

Another option especially if the scope used is a little longer is to do the same as Joel Dorleac does with many of his rifles where he machines up a custom rear sight base and fits the claw base in with the rear sights. In this case one could also use a Recknagel front ring pivot base and use the Recknagel front rings and a Steyr type custom rear base and ring.

I am also looking at how to fit a small catch at the bottom of the magazine box to catch the En Block clip as it comes out so they don't drop onto the ground unless you want them too but rather can be released into your hand when you want to catch it. I will report back on that one as I have a few ideas.

Matt.