Weaverbird : Loop Subdivision question

Hi all, 

I've created the initial with this function but there's one or two places I'd like to have more control on, in terms of thickness and angles.

But I came to realised that tweaking these whilst keeping the original matrix wasn't as simple as I thought,

I was wondering:

A. if there's a way to 'loop subdivision' only the surface, keeping the top and bottom angle at right angle (see photo attached - A)

B. thickening the branch between the two voids (left) without thickening/minimizing the thickening effect on the other branch (right)