D'oh....too few coffees....
I set up a Bus and used it to apply the effects to the track...works, naturally.
I think the way I sometimes apply fx to individual tracks in Acid led me to think the same would work in SP....but no...it's a little different.
It's a bit like "...hey, I don't need to make this effect available to every track...it's part of the sound of the "instrument..." so you just apply it to the track....like putting a delay pedal on a guitar....but that approach doesn't seem to work in SP for delay-based fx, at least....due to the clip length thingo....
In short...all delay-based fx should be given a Bus, then feed it whatever track you want to effect. Just like a mixing desk!