The mulihull equivalent to the 29er would be a scaled down Tornado. The F16 or F14 could certainly be marketed as mini-Tornados but we would still miss the multihull equivalent to an Optimist.

I see it as a small one design cat powered by a simple rig, able to beat an Optimist in some key features:

-safety
-simplicity
-rigging time
-beauty
-price (if possible) and
-performance ( but not too fast, just enough to comfortably beat an Optimist. Parents prefer toys that keep kids within a manageable distance.)

An F12 could be the answer.

Lastly, both the Opti and the 29er are one designs. This gives a perception of "lower price and lower maintenance cost to remain competitive and get a reasonable resale value". We know that in the long run it isn't true, but the key for sales is "perception".