A bit "Ouch" Dan http://www.waffencenter-gotha.de/sho...8_265_376.html
But there is a chance a base will come up on the bay and you can buy the plate-----------OR if you get the base then you can file down the plate off a B2 and drill and tap it for a screw for elevation. I did this on an old Diana . TIP-----drill and tap to one side of the plate and not in front of the notch or the screw head can come into your sight line.