Profile Extrusion (sweep 1) problems

I have uploaded a rhino file I am working on as a test for a joinery project.

I have created a square edged arch (timber garage door frame) I now want to add a profile to this edge a simple ovlo, The method I chose was to draw the profile and sweep it around the arch and then I would cap it and then Boolean difference to create the profile much like using a spindle moulder to achieve this in the real world.

However it doesn’t cap, I have tried this a few times without much success what am I doing wrong?
I would need to be modeling timber profiles on a regular basis so a suggestion of another approach/method or some tips for stopping this happen would be much appreciated.

thanks

3d test.3dm (202.5 KB)

Seems to cap and difference out OK here… --Mitch

Cap-BD.3dm (173.4 KB)

Thanks! clearly I got that wrong… I just tried it again