Laev has lousy article indication in tracking -- something I'm told is perfectly normal for her age, but that's no reason to just let it go. :-) I also want to start teaching her a down contact behavior for agility. I think I'm going to combine them.
I like the accuracy of a 2on2off contact, but I don't like the impact that it *can* put on shoulders if the dog doesn't rock back properly. Laev's puppy agility work encouraged her to rock her weight to the rear, but she's going to have a high-impact career anyway (slamming into decoys, scaling 6' walls, jumping 39" for retrieves) and I'd rather not add any more stress than necessary. So I've been seriously considering starting her on a down contact behavior, hitting the dirt just below the contact zone.
And I can combine this training (down on a target) with outside article indication (down with nose on article), which I hope will strengthen both behaviors by adding variety and generalization and offering a greater number of high rewards for correct response.
I don't know that this is a perfect answer (a running contact would be even less stress on the shoulders, for example, but I really doubt that's going to be achievable with the Laev!) but it's the current plan.