Dovetail will work well on an over and under where you can easily get to the dovetail to tab the mounts in sideways, or if side by side the Rib is quite high. Much more of a problem if the rib is more of an English style sunken concave rib that is lower then barrels - you would n't be able to cut a dovetail into the rib to drive in the bases. You would probably then require some sort of bases that could be let into / sweated onto the sunken rib. If you have a look through the Eaw or Recknagel catalogue you can see all the different types of bases that they do.
Heym SR20
