Fuel volume is a problem. When I used the bladder, the airplane was built in 1975 (old rules) and had developed a fuel-foaming problem. The bladder solved this. But in those days, low speeds, even later in the '70's, were not all that slow, so I got away with the limited fuel supply then. I can't imagine getting the 10+ ounces of fuel required into a bladder these days.
Pete