I think narrow diameter chambers work better with flakes in general, and especially Va flakes. I use wide diameter chambers for Burley blends (for me that's mostly C&D's Haunted Bookshop and H&H's LJ Heart Burley). For a blend that's new to me it's pretty much an experiment, and I consider that a wide chamber will admit more oxygen per puff, producing more smoke volume. If the blend has killer nicotine content, it's back to a more narrow bowl. I consider anything greater than 13/16" (~20mm) as in the wide bowl category.
I think wide bowl pipes also favor the more aggressive puffer. I don't see how you could keep a large diameter ember going if you're a "sipper".