Well, it's very strong (a somewhat hard to define word -- it has high stiffness and is damage resistant due to the containment quality of the fabric skins), and surprisingly abrasion resistant. Not that I intentionally try to abuse it.
As an example, I was out in some nasty stuff on Lake Champlain two weeks ago -- I got caught out from an island we were camping on, with wind speeds over a long stretch of open water at 10-20 mph gusting, and waves building to small whitecaps. I had no problems with maintaining control and course at close to 90 degrees to wind and wave. Very buoyant and it rose so well to the swells that I didn't take a drop of water on board. After five minutes of it I felt quite comfortable, and not worried. Took me a couple minutes more than normal to make a crossing (I made two I was so confident after the first one.) It really handled well. I had aboard maybe 230 lbs total with my own weight, anchor, fishing gear, and ferried supplies aboard, so with the boat weight maybe 260 lbs.
In equivalent conditions once in my commercially built kayak (Lifetime Tamarack Angler) on the same lake (it's about 100 miles long and 13 wide btw -- not a pond!) last summer, and at about the same weight, I was definitely worried, and wet. Took on plenty of water. I had to quarter into the wind and very slowly crab sideways to my intended landing point about a mile away, and that took me a half hour of carefully white-knuckling it. I had to constantly correct and frequently point up into an oncoming wave if bigger than normal, then swivel back to quartering. It was definitely not a fun ride.
I should say, both times there was a relatively close and friendly lee shore, and I had a life preserver on, so there was probably little ultimate danger, but nobody wants to dump, lose all your gear, and have to get rescued or walk to someone's house asking for assistance.
Flier is quite strong and stiff, and has built in abrasion resistant reinforcing on vulnerable areas. These are an important part of the design more fully detailed on the plans. Foam covered with fabric seems to resist dents much more than you'd expect, and if dented has essentially self-healed on my boat. After 25 fishing trips it really looks like new. But even so, serious damage would be very easily repaired with this construction. Just cut out a rectangle bigger than the damage, splice back a matching chunk of foam and patch over with cloth, and then paint.
One thing in its favor re. hangar rash, is its light weight. Twice, due to wind, I've accidentally dropped it sideways off of my car roof racks onto a hard packed gravel parking lot. At only 27 pounds on 12 feet of length, it just bounced on its side lightly with no damage. And I've put about 5000 miles on it atop my car, including two 500 mile journeys and two 150 mile jaunts so far. There's a lot of wind pressure exerting upward force at 65 mph on an inverted boat atop of a car, especially stuck behind a semi truck throwing turbulence. Add to that crosswinds at times and a boat like this one is probably withstanding more breaking forces than it does rowing in waves.
I will say this isn't a whitewater boat for bony rivers -- I'd take an ABS plastic canoe for that, by preference. But of course, that wasn't the design intention for Flier And it does have the advantage of half the weight.
This boat just works, for me, at least.