Contact John Taylor Taylor Machine Works http://www.johntaylormachine.com/.

I had thought Vic had closed up shop.

Tell John what you want done. He will do it.

There is the American school method of welding up the striker hole and making it offset.

Or the way BSA and the way in the British Army Martini Armorers manual of lengthening or shorting the ears of the lever to move striker hit up or down.

You are better off telling John what your want done and getting out of the way..

As far as switch barreling a Martini Unless your two cartridges are similar you need to have two different trigger groups set up with different extractors and adjusted for the different load heights-load position of the breech blocks.