The Rhinoflex 15 is very snug in the Casita
16's bumper, you have to be sure to fully compress the whole hose /before/ you put the airtight end caps on (or just leave them off and deal with the inevitable dribbling), and store the separate orange drain fitting piece in another compartment (mine fits in my battery
bay). you need to rotate the ends just so to fit in the square bumper, too, so the 4 'tabs' are at the corners, and so the right angle end is horizontal or vertical.
pretty sure the scamp
13 has the same size bumper...