Slight hijack here, but worth mentioning:
It is easy to improve the Greener side safety for 'safer' performance on a potential DG rifle.

As produced by William Wellington, the safety is probably quite OK for a shotgun, but once the checkering gets worn a little smooth, and we add some sweat or slippery blood, that thing becomes very difficult to operate, and on a DG double could get you killed.

Here is a 'before and after' photo of the modification done to my Greener .577 by Rolph Bachnik, long before I acquired it I might add. It works perfectly and I would certainly have this done to any Greener DR or bore-gun conversion in the future. Being non-automatic already is a bonus too.