...the side force on the sail is roughly 43 Kg (421 N). Each foil will have to supply 10.75 Kg of side force and lift 37.5 Kg (367 N). So your ratio of vertical to side force is 37.5/10.75 or an angle of 74 degree...
In practice the boards are designed, angled and placed so that their lift resultant points toward the sails' CE in order to minimize (neutralize) the heeling moment. In this case they are true "Bruce foils".
I believe you will need less than four 1m boards at work to fly an A Class at that speed. Maybe half of it. Also, it makes more sense to use one slightly larger canted board aided by a small horizontal foil in the rudder.
