thanks rick. dont be afraid of the water, life guards are on duty.
as for the plugs i made them a tiny bit bigger than the square and tapered the ends with a chisel. so when i pounded them in it was a tight fit with no rough edges.

 I think that is to the bottom of the pillow curve where the flat begins. 
this is what i did.

working with my hands is a joy,it gives me a sense of fulfillment,somthing so many seek and so few find.-SAM MALOOF.