Adds Instant lift - Changes a 'sticky' board that is hard to get off the water onto foil earlier when dogging. If your foil base plate is parallell to your boards flat bottom - this can make them feel like they 'stick' to the water a bit when being pulled by tow or Parawing forward (As this sinks more weight onto your front foot - changing the foils flight  plan into a downward direction)
Mast shim corrects this. 
Boards with a lot of rocker and a Negative mast plate angle also benefit immensely. 
 
We've tested 1 degree one and a half degree and 2 degree, majority of Parawing boards benefit from a 1 and a half, while SUP foil boards can be up to a 2 degree shim, with exception of the 'Frank ' boards which have this built into their shape.