I would strongly prefer to have the boom above the attachment points of the push rods as then the rig can rotate fully around the mast which is very advantage (performance) when sailing deep. It also is a safety feature as any kid can let the rig weathervane completely when surprised by a squall or something.
A freehanging boom (possible with a fork at its mast end) is possible and most easy solution.
Not sure a reduction on mast height gains us much as its such a small triangle at the bottom that you gain, and that doesn't lower the COE very much. And I tend to agree with Wouter about letting the sail weathervane if required.
Also, don't see that the stayed rig is that much more complicated, but do agree that the freestanding is faster & easier to rig.
To my surprise, most who I have talked to so far have elected to go after the stayed rig because it will allow trapezing, and these are the kids talking, not their parents who don't seem quite as sure about the whole thing. In the words of one kid.....why should I hike all day when I can trap and go "zoom"
You are both right. Besides Optimists, I sailed with fork type goosenecks in Penguins back in the 70's - with rotating wingmasts! It is very simple, efficient and inexpensive for small boats exactly as you say. Note that it was not possible to weathervane the Penguin due to the shrouds (unlike the Optimist), so the fork solution is ideal for the free standing rig only, not so for the stayed/trapeze rig.
Two divergent conceptual paths (trends) emerged and are being followed:
a) Simplicity oriented, with chined hulls, free standing rig, hiking straps, cheaper price. It is essentially the original F12, but I'll call it F12 One Design.
b) Performance oriented, rounded bottomed hulls, stayed rig, trapeze, normal price. It is essentially a Mini A Cat.
I guess it is ok to follow both trends until a clear winner emerges. Still, we already know that the Mini A Cat will end as a scaled down A Cat, so we could just as well follow the F12 One Design path only and in the end compare everything to a scaled down A Cat - including the class rules.
I made my own spreadsheet to rationalize the decision process and it indicates that the F12 One Design wins by a small margin, basicaly due to simplicity and costs. The other differences more or less cancel themselves. Sorry, could not upload the spreadsheet as is, just its picture.
