I agree with the quality of the Calvert design but would never buy a sail from Dave again due to the fact of the customer service. I had a sq top made for my 21se which was beautiful but needed some things added that they forgot. I sent it back, they made the changes and sent it to the wring address and it was never found. THEN Dave Calvert (after over a month of calling) wanted ME to pay for a new sail. Aside from that, they make a great sail.
I think Elliot Pattison has the most experience with the boomless square tops. Not my first choice of sailmaker, but the most exp with this style. I have attached a photo of my Calvert sail on the 21se and my buddy's 5.8 boomless/sq top made by E/P. Lee