this is the 4 ft. board i will start with , out line from mojo , and i think i will go with a square tail , the board will be 1'thick with taper to nose and i will try a 2' rocker for the nose.name phlaunder for it being fat and flat. ahahaha
Square vs the swallow? If you leave the tail width the same I doubt you'd feel much difference with or without that small void in terms of stability.
If you look at the nose of most popular skimboards they are basically a pintail. When that type of board is ridden revert (fin first) the pin will sink a bit and that affords greater stability even without a fin.
IMO, the squaretail would be easier to build and laminate for a first effort.