FWIW: Hitches have plenty of safety margin at their rated max, so I wouldn't be concerned about loading them to the max. Also, the tongue weight limit is allowable at max towing load limit which includes fore/aft, left/right and up/down loads placed on the hitch by the inertia and momentum of the trailer under acceleration, braking, cornering and bumps. With a hitch rack, the hitch is only dealing with the mass of the hitch and bikes and not a much more massive trailer pushing/pulling on it.