With a lot of help from this forum I have thoroughly investigated the available options and decided which way to go. I thought I should share it here for the benefit of others.
I have tried using .WMF files to provide borders on text boxes but I just can't get the quality I wpuld like, mainly due to-
1. Pixelly jagged edges on curves and diagonals
2. Can't surround it with a different colour border
3. Difficult to get the text lining up really well.
I have tried all sorts of combinations with color gradients etc but can never get it quite good enough.
Using vectors, on the other hand, gives brilliantly clear-edged shapes, with borders if required. It is very obvious why Digital Workshop has decided in V4 to use vectors instead of WMF files to define text box border shapes. Good move guys!
The vector editor is, in my limited experience, brilliant. It makes it relatively simple to do a job that would otherwise be practically impossible. By creating some key shapes and saving them in a gallery I can avoid having to repeat excessive "fiddling"
Until I can justify the upgrade to V4 I will use another valuable feature of OPUS and create a gallery of useful vector shapes.
Once I have the key vector shapes I will "frame" text boxes on to them and create a gallery of commonly used speech balloons.
I will then have the tools I need to get some prototypes done.
Am I on the right track?