If we were striving to keep the boats within a certain PN number, nobody would ever bother building a faster boat! True formula racing says "Within these guidelines, all boats are considered equal. First across the finish line wins." As stated before, I'd rather sail Portsmouth and sail fast, than build a boat that already has it speed limited by ratings or weight.
Under the current rules (which are still subject to change), a H14 owner can switch to H16 beams and mast, trapeze rack, and toss on a huge headsail to try and beat out the rest. There is a point where beam becomes excessive and the leeward hull is no longer able to support the loads placed on it. The 18sq. class found that 12' was about ideal for their length and sail-area.