I have never seen any fins like these. Anyone seen them before? Anyone know about their maker, whereabouts, what they did… anything? Thanks. http://www.surfline.com/surfaz/images/foo_mark/chang_mfoo_port.jpg 
I tried the rear boomerang fin in the 80s and didnt care for it. I have no idea of the origin or ideas behind it though.
The side Fins are freesyle fins, they have a thinner box and are adjustable forward to aft Via a tang on the fin and ridges in the box.
I believe I remember also Bobby Owens riding them when he lived on O’ahu. You might try contacting him at the Patagonia Outlet in Santa Cruz - thinks he’s the manager last I heard. The Willis Bros. may have initiated the design. Can’t recall for sure - if it comes back to me I’ll post it. Aloha.
Me again. Thinking about your question for the last few minutes and remember the windsurfers back home on O’ahu. I think you need to focus your research on the sailboard industry. That’s the origin of the fin - Bobby Owens was probably the first to adapt the design for surfboards. Hope this helps. Blessings.
MacElheny sunset beach Football fins…Sickle fins…boomerang fins…experimental Junket 82? 83? co- opted by by north shore"" residuals to set them selves apart from the main stream …when the main stream kept flowing with the moderate take they faded and went away the moderators win always the mass mentality only accepts so much change at a time…goal was eliminate cavitation…that not over come they went to slots fingers and fore fins { reverse that order)…I got two sideies 3 1/2" want em …whadda wanna trade?they are root beer brown or bring your board over an’ try em at hanalei saturday ambrose…boomerang sideies
mcelheny, there’s a name i haven’t heard in a while. a buddy of mine was sanding for him back in the 80’s and asked me to go hand sand some of his sailboards up at his place in pupukea. he had some mad design with these concave rails, kinda like concave chine rails, that required hand sanding nose to tail. afterwards it was the 40 mph death ride down the pupe’s hill with no brake on my mountain bike (but that’s another story). as for the boomerang fins, i tried one on my 6-4 back then, it went alright, but if your leash gets in front of it, it gets tangled and you get this weird hydroplane effect.
McCoy makes boomerang or gull wing fins as he calls them. Check out http://www.mccoysurfboards.com under accesories and fins. Also some describtions of the fins under design. regards, Håvard