What i do is sit her beside me,throw the dummy, wait for a moment then send her.
She goes straight out and picks up the dummy, at which point i run backwards and get right down low when she approches.
We only do 3 or 4 retreives per session and i try and make them a bit difrent each time ie- hide one in the grass etc. And always into the wind.
If I sit right down on the floor with my legs open when shes returning she'll drop it right between my legs but never to hand.
NTTF- what do you mean by a bumper ?