I'd check with Ford. 100 pounds is well within the limit of my Plymouth
voyager. (I think it is 150 pounds) I had an Isuzu trooper, which was labeled
for 200 pounds. You might have trouble with the width though.
I recently loaded a Perception Kiwi 3 (open tandem) and a Swifty (single) onto
the van and had to "tilt" the single because the rack was too narrow. Each was
then secured to the OEM rack with two ratcheting tie downs as well as bow and
stern ropes tied to the bumpers.
The boats didn't move but they did hum annoyingly at highway speed. (Picture
blowing across a soda bottle) I reduced the sound by re positioning the boats
but it was still there. Good trip anyway!!!

I have a small recreational sit-on-top kayak (Wilderness Systems
Tarpon 100). Its 10 feet long for about 50 lbs. I want to buy a
second one for my wife. We have a Ford Windstar van which can easily
carry one on the roof-rack, but two is just a little on the heavy
side.