Never tried double foiled fins on a quad, but then again I’ve only had one quad. My concern with trying double foiled fins on a quad is that a double foiled fin may not favour either rail or is neutral as I like to put it.
The reason being (I think) is that double foiled fins are double foiled. Not single foiled. I think a few posters have mentioned double foiled fins and quads before but to my way of thinking a double foiled fin belongs in the centre of the tail like on a thruster or single fin. Not out on the rail like twins or quads.
Feel free to tell me I’m talking out of my avatar.