Revit door and window families with splayed jambs/surrounds

I needed to make up some door and window families with splayed jambs typical in northern UK 19thC and earlier traditional vernacular

I tried first by modifying a door family with a void sweep profile and selectively subtracting. But it wont - you get a cant make message saying you cant cut from a hosting family which contains an opening (as you start off with in a door or window family template.

The solution is to get rid of the opening in the template (just tab in elevation until the opening geometry is highlighted and delete). You should be left with a solid wall and a few ref planes.

Then form the opening with a void extrusion locked to height, width and ext-int ref planes. Pick the void and use the cut- geometry tool (Mod-geometry panel)

Then form the splay as a void sweep - the Sketch Path is locked to the outline ref planes and Edit Profile to sketch the splay profile locked with params to control the angle and dims. Again Cut Geometry to finish

Only then form the door and door frame as void forms cut what was there before and not what follows. If the void is cut after the frame the latter will disppaear and quite complex to slectively un-cut.