Paul,

I will let you in on a secret.

A standard Taipan sail was NEVER 13.7 sq. mtr. even if some webpage claimed it was.

A standard Taipan 4.9 mainsail including the mast section is typically 14.54 sq. mtr. So roughly 14.5 sq. mtr. Subtract about 1.4 sq. mtr. for the mast section and you'll end up at 14.54-1.4 = 13.14 sq. mtr. pretty close to your 12.9 sq. mtr. I say !

Also the area for a standard Taipan mainsail was never ruled upon in the standard Taipan 4.9 class rules. They only limit the luff, leech, foot lengths and the width of the sail in 4 places. So there can be some variation in the overall area between compliant Taipan main sails.

For F16 is is just maximum 15.00 sq. mtr. including the mast section and as far as the F16 class rule is concerned your leech may have the outline of a teddybear if you think that will make you faster. Those additional 0.4 to 0.5 sq. mtr. area will all go into the larger squaretop.

Wouter