It can be a big deal. The idea behind the canted board is that it helps provide lift on the leeward hull resulting in less wetted surface area. There was an F18 a couple of years ago that had boards that were seriously canted (something like 30 or 45 degrees!). Canted hulls are not allowed in F18 and the rules were later modified to require the daggerboards to also be in the same vertical plane as the hulls. Orma60 Trimarans and the C-class catamarans have taken the canted board concept to the extreme with the 'bananna boards' that are circular in shape - the concept works. Next time you look at an Orma 60 trimaran, consider the tiny size of the amas and ask yourself how they could possibly fly two hulls on that tiny little ama. The canted (bananna in this case) board provides the lift to give the ama extra height in the water to be able to carry the load. Somewhere I read that the optimum lifting board angle points it's lifting force at the center of lift provided by the sail plan.

With regards to the A cats, their rules prohibit the use of "hydrofoils". However, the term "hydrofoil" is not defined very well but is assumed to infer something with a t-foil shape (like the Moth or Windrider Rave has). There are those that feel that a canted board, because it provides lift, falls within the definition of "hydrofoil". It's a big grey area and it looks like Ashby was willing to test it.