I think the biggest issue with foils on Islands is more to do with sail area than weight, a standard TI has 90 sq ft of sail, an H16 has around 218 sq ft of sail and an F18 has around 450 sq ft, however the TI is larger than both of those boats. Most of the glass cats are in the 300 to 400 lb range, and the TI is about 200 lbs. With just the standard sail, my standard TI simply doesn't have enough sail area to get enough speed to get up on my foils (even with my 33 sq ft wing jib included), plus you have the dreaded double drag problem, where you have the drag from the hull and the foils in the water before you get up to lift off speed (about 8 mph), even with the foils locked in neutral (zero angle of attack) there is still some drag there. The other problem is the TI hull is a displacement type hull that max's out around 8 mph, above that speed the HP required to propel the boat faster goes up exponentially where with the cats the length to width ratio (L/W) of the hulls is typically greater than 8 to 1 so the displacement hull rules don't apply to cats, they are call modified displacement type hulls and different rules apply (basically it's harder to form a bow wave on a hull with a L/W ratio greater than 8/1 and impossible on anything greater then 16/1.... why cats can go very fast). The boat in the video has very narrow hulls so the displacement hull rules don't apply.
Personally I only like to go out when the water is fairly flat, and the winds are between 4 and 8 mph (typical winds around here). Around here anyway when the winds get above 12 mph, the waves get very large, and it gets very choppy which make riding in the TI very uncomfortable for me so I end up staying home is the winds are over 8 mph. The way my boat is rigged, I get maximum performance from the boat in 4-7 mph winds, where the boat in those winds averages 8-10 mph (about 1.5x to 2x windspeed), which works out very well for me. I still have my hydrofoils and once in a while if the winds are around 15 mph, I throw them on and go out and foil around, but with the setup I have I can only foil down wind, by deploying my 135 sq ft spinnaker (about 260 sq ft of sail total). The downside to spinnakers (why I very seldom use mine anymore) is you cannot go any faster than the wind with a spinnaker, because it works like a parachute. So in order to use my foils the wind has to be over 12 mph, and I can only foil with the wind behind (90 to 270 degrees), so to me since I don't like rough water so much because of my bad back, I never bother with my foils anymore , it was a fun experiment, but not practical for me everyday. If I had something like a wildcat or F18 with a ton of sail area to work with, and really good sails (and boat design) to begin with, I think I would have been way more successful with foils. Just too much to overcome (sail area wise) with a TI and foils in my opinion.
My advise to anyone who wants to mess with foils is, if you have a sailboat that you can get to 20 mph in 10 mph winds (2x windspeed), adding foils can possibly get you up to 3x windspeed (or more), but you have to have the fast boat with efficient sails to start out with, anything else (like trying to foil a TI) your just wasting your time IMO. You can't make a racecar out of a brick (LOL)
As always it's always fun for me to design and build all this stuff, but it's more for something to occupy my mind and hands, than anything practical. Money is another factor, I doubt you can touch any kind of boat like a Wildcat or F18 for less than around $15k to $30k, I just don't have that kind of money. Total cost for all my sails, hydrofoils, and everything was only a few hundred bucks, plus a couple weekends in my garage (I design and make everything myself as part of the hobby).
my 2 cents