Trouble with Boolean Diff

 From:  Mike K4ICY (MAJIKMIKE)
Hi Steve!

You could try to make sure that as many of the type characters are Unioned or Trimmed-and-Joined into a closed curve before Extruding them.
It looks to me like there are a lot of strange overlapping elements.

It might be best to even do the Boolean Difference to a flat 'reference' shape first - and then Flow that.