on flat vs. full... design question
A basic design element is the depth of shaping cut into the sail.

Some designers opt to shape the sail body generously with seam shape. This approach may work well in specific wind ranges, although testing indicates that such designs may narrow the effectve wind range.

Full shapes cut into the sail body are difficult if not impossible to remove; a flat sail body is a requirement for upper end performance.

The Loft designs sails with forward shape orientation and a flattish sail body with generous mast pocket rotation/mast overlap.

This configuration can be made effectively full with release of outhaul tension.

Sail shape that de-rotates into the sail body from the front of the foil produces a large wind range and a comfortable stable feel.

Sails can include both low-end power and ease of use in the upper end if the design anticipates trim impact; trim sensitivity designed in.