One more day of Christmas over-indulgence tomorrow and then maybe we'll get back to more normal, I hope.
There have been some interesting thoughts on my question, and I'm glad to see that my 'alternative' idea has also appeared, but first let me try to clear up come confusion I seem to have started with the Amiina Mk1 and Mk2 rigs.
Edward got the boat in a run down condition and ideal for a conversion. We had the sail diagram from sailboatdata.com, but the sail area was based on 100% foretrangle and not 'real' sails. When we asked around we found that the sailmakers and racing boys were not prepared to divulge their 'secret' numbers, so we approached the Van de Stadt design who told us over the 'phone that the full fore and aft rig was 220 sq.ft. so I drew up the rig and wrote the instructions for a professional sailmaker to build the sail at that size. The boat sailed well but seemed tender, over-canvassed and had to be reefed early.
The big shock came when the handicap for the Round the Island Race handicap turned out at 0.833, similar to an Elizabethan 30, and faster than the Contessa 26 and even a Hunter Sonata. Something was obviously wrong. Even so, with that handicap and in the first attempt we came 305 out of 681 to finish and reefed down quite a lot of the time, and in the top half of the fleet.
The handicappers will not give out their formulae so we had a search until we got our hands on the IOR rating certificate of another Splinter, and found the sail area was only around175 sq.ft. The following year Amiina sailed with the bottom panel permanently reefed, and the handicap improved to 0.786. Of course the weather did not play ball and none of the smaller boats completed the race.
The next year the bottom panel was reinstated and the top panel was removed, so only the 5 parallelogram panels were used. And yes, the rig did not exactly look pretty being squat and square. With this low aspect ratio rig they came 188 in a fleet of 701 boats, so about 26% down the fleet, which is very respectable when you see how much the light boat is stopped by the chopped up sea state during the race.
I drew and built the smaller 5 panel Mk2 rig for the following year, and the handicap dropped to 0.776, but again the weather let the smaller boats down so it was another year before a race was completed. When Amiina raced the following year they were 107 out of 647, or 16% down the fleet, which is very respectable.
What is of interest but not possible to confirm with results is the performance when the wind was light and the small boats could not get through the tidal gates and complete the race. In these light conditions Amiina was always well up with bigger faster boats when they had to retire, even with the smaller Mk2 rig. Amiina is a nicer boat to sail with the smaller rig, and I am not surprised that everyone uses about 175 sq.ft.
It is hard to put in words the confidence that the simple to sail rig gives. I know it's not perfect, but those who stick fairly close to the Amiina Mk2 all seem happy with the result. I hope this helps to clear the water and does not muddy it more. Don't forget, the aim was not to build a rig for racing, but that the RIR was thought to be the best way of sailing alongside cruising boats all trying to go in the same direction with the same intension. Even if our tactics were wrong (and they generally were) and we were in the wrong tidal stream for a good overall race position, we were still sailing alongside other boats, often bigger and faster and were able to see how well the rig performed. It is satisfying to sail tack for tack with a Westerly Fulmar who started 10 minutes before you when some 4 hours into the race.
I'll post this now, and write further on my questionable ideas soon.
Cheers, Slieve.
PS. Please note that Whisper, in the PBO report is a highly tuned boat where the owner is prepared to lavish expense and effort beyond the normal for a simple cruising boat. No way like for like.