Hope you find your dream unit; as far as I know all trailers are measured from bumper to tongue tip.
Some overhang the rear bumper like ours and still others over hang the tongue, we had a trailer that did that back in the 60's
is in the body so if you want 17' floor inside think 20/21 outside for most makes
We looked at an Rpod they have a canvas fold out in rear and my wife wanted "no more canvas", and it was too heavy for our car. What you loose in the tongue you get back in the canvas pop out with an rpod. rpods are very nice units to be sure