There are some fairly detailed length limitations on the sail area and cut lengths. I am not sure how the H16/P16 masts would fit into this measurement system, as I do not know their measurements/lengths. It may require a completely new rig (which bites, see N5.5 SL converting to N5.5 Uni). Check out http://www.formula16.org/ for the complete set of F16 rules.

Competitiveness would probably all depend on the sailing conditions, but given equal sailors with equal opportunities/upwind/downwind/reaching legs - I'd put my money on a full up F16 compliant boat that was designed from the ground up (Blade, Stealth, Taipan F16).