Ah, but don't forget these things were but a forced development of the old "seat on wheels" open carriages of the early days, and also that as far as the Ministry were concerned, they were only ever appliances that just happended to develop to look like cars. After personal mobility for the user, luggage space & such-like were way down the list of considerations. The space in a Model 70 or other full-bodied conveyance is there primarily for a folding wheelchair, not the week's shopping....
Why do people always go on about stability with these things? All I can say is very few who raise the subject can actually ever have driven one any distance. I have, & you'd have to be doing something pretty damn silly to get out of shape with one as the centre of gravity is several inches below ground level (or so it seems) and being sat in the middle of the chassis, weight distribution is as bout as good as it gets.
Also, those who think a Model 70 is slow, think again. Compared to the old Villiers-engined stuff & even to a lot of vehicles these days, they were & still are veritable little hot rods....