Boolean woes.

 From:  d^^b (DAVID)
3982.3 In reply to 3982.1 
Hello DannyT:

In your example, the solid is no a volume, but a polysurface, isnĀ“t it? Then, there are only two surfaces for work in.

Maybe only a trim command is enough for get that you want.

Sorry if it is not the question you were looking for!

Edit: You have discovered the answer yet! :-)