I am hoping by 'spinnaker chute' you mean 'snuffer' as is the term over here, for in the US you've just used two terms for the same thing ;-) 'chute' is the nickname for 'spinnaker'

In any case, you'd need to go to the Farrier sites to find out for sure about the class legality. I can't think of any reason why, except the sprit isn't really long enough for the snuffers I've seen.

Alternatively, I guess you could install a 'spinnaker sock' which is a cover sliding down from the masthead attachment over the chute, but eeew, the windage...

Personally, I don't run a chute if I'm shorthanded, and shorthanded to me is two on board. I use the screacher instead. Maybe if the wind is real light I might call for the chute if one other is on board, but if there's just two of us, we're cruising, and who cares?

Others' mileage may vary...