Sorry SX wings because they extend beyond the cross beams
Is the main bigger for the SX?
Yep, SX wings are longer. Also, the main AND jib are larger
According to Matt's 18 specs in the FAQ post, the SX version actually has less sail area than the standard H18 (240 sq' for the standard vs. 220 sq' for the SX). The SX has a taller, higher aspect sail plan but assuming Matt's figures are correct, it isn't larger.
'82 Hobie 18 SE with '85 Nationals Prism (White) sails
'73 Laser HID# 3463