Originally Posted by
RandolphCarter
Going from a 126mm rear hub to a 130mm rear hub won't impact the frame spacing at all.
Um what!? The 126mm and 130mm ARE the frame spacings. I don't catch your drift.
I do however agree with your comment that a freehub makes much more sense than a freewheel hub for a heavy person.
My suggestion is that the first step is to ascertain whether the frame is actually 120mm or 126mm by pulling the wheel and measuring between the dropouts with an accurate ruler. Then, if it truly is 126mm, find a 126mm freehub wheel with either 6 or 7 cogs.