I all dependents on the specific makes of the catamaran. I know of an 18 sq. (also an 18 foot boat) that had trouble sheeting in the spi and I know the I-17 guys overhere changed back to a single forestay. My bridle wires are much further back then those on a FX-one, so I could be fine while the FX-one won't be. There is no general rule that predicts who will have trouble and who won't, dependents on specific implementation.

Also getting a longer pole is not always a solution especially not on an A-cat whose daggerboards were never positioned with a spinnaker in mind. You can upset the balance of the boat.

I'm sure some designs could be in the clear. Nevertheless this problem can arise and has arisen on several boats.

It is definately a thing to keep in mind.

Wouter