27 oz of fluid for fifty miles. That must put a lot of stress on your heart as your plasma thickens up from loss of fluids.
Maybe not, but I've always felt that being stingy with hydration would affect how thick your blood plasma is.
But heck, if you can do a five hour 100 miles, then good for you. I couldn't do it solo, I'd be over six hours. Maybe with a decent group of seven or more that are used to each other and pulling turns.