I also sail a Stealth without T-foils although I have on a few occasions borrowed a pair.

I don't believe they cure the "nodding dog syndrome" - that's based on racing alongside a T equipped boat and noticing that it was pitching up and down in the same way that my boat was. Mind you, we do get a pretty nasty short chop quite often which doesn't help.

I've always thought that the problem would be with the increased drag in light winds. That doesn't appear to be borne out in practice however with boatspeed for "T" and "non-T" boats being very similar.

I've not noticed any additional problems with weed. Where I sail (the Firth of Forth) the problem tends to be with floating seaweed around spring tides. Whilst the damn stuff does get caught on the rudder and usually requires a guddle over the back to clear it, I've not noticed any getting caught on the foils.

If you hit something with a cartridge rudder (with or without foils) something may break. But as you'll have already hit it with the daggerboard you probably won't be going too fast!

I've only briefly sailed with T-foils in strong breeze - about an F5 as a squall line came through as I was on my way out to the race course. In those conditions you cannot understand how amazing the foils are until you've tried them. There is no tendancy for the bows to dig in at all (even with no spinnaker up), you just make the boat go faster!

My conclusion is that in big breeze the T-foils are faster because they let you push much harder. In light breeze I don't think they're faster - but I'm not convinced they're slower either!