Thanks for your help. The four words that made the difference for me were, "move the mast upwind". That has cured the rounding up problems that I was having. I guess that I was sheeting in, but not keeping the ceter of effort of the sail over the right spot of the board.
The reasopn that it has taken so long for me to get back on this was because the I haven't been out in conditions that let me try this out.