Spinnaker bags and pole end snuffers were all the rage when we first started w/ the spis on our Taipan's. Way back- remember Wouter? I still have my first pole end snuffer I put on my 4.9- That's very easy to snuff/deploy but the added weight and particularly windage kills you upwind. And as you have often commented on in the past Wouter, you spend more TIME sailing upwind then down, so a 5% difference in upwind speed between 2 boats, even at the cost of a 5% difference downwind, in a straight windward-leeward course (currently the most common over this side of the pond anyway) will have the upwind advantaged boat first every time. Mayhaps I am a little "different" (many people will confirm that BTW! Probably what helped when we started this F16 circus!) in that I regularly sail both an "A" cat Flyer and F16 Taipan, so I'm quite cognizant of the differences- Getting a good start is also a critical thing and getting clear air up the first beat is important as Wayne mentions, and nothing like being able to start anywhere on the line, like in my "A", and if on time having clear air quite quickly and being able to force anyone above you to tack off or go slow until you "gas" them- also results in an "intimidation" factor in small fleets- they pretty much don't WANT to be above you and will give it to you. Also, on a very short course or in very hectic conditions, the "A" will kill you because they don't have to worry with pulling OR dousing the spi and can more quickly get to their max speed up/downwind.
So of course it's all a trade off- Trick is to trade the least off- That's why spis SO FAR have gone from bags (still commonly used on distance races BTW because there the complexity/weight/windage of any snuffer is not worth it since the spi is rarely launched/doused relative to sailing time), to pole end snuffers, to midpole snuffers.
Another option perhaps worth exploring I've thought of is a retractable pole/snuffer combination- retractable poles are now very common on monohulls- again question is are the tradeoffs in cost/weight/complexity and sailor's time/thought/effort worth the gains??
These are some of the things that are fun when playing in a Formula Class!
If the "A"'s as a class adopted spinnakers I assure you we'd see some interesting developments! Gregg Goodall even suggested a "tacking" spi pole to me- haven't tried that one out yet either.

Kirt