[ProudVet77]

As pointed out by another poster, if you use a V shaped grill it will leave groves in the breast. A way to solve this is to use small cookie pans on both sides of the V. Or you can prop the turkey up with crumpled tin foil balls so it rests only on the top of the breast. It's worth the effor. The meat is so much juicier. Also the stuffing flavor permeates the breast meat.
One last thing, be very careful turning it over :)

[Mjaye]

When I first heard of the upside down turkey some years ago, I wondered why a couple of new, big sponges couldn't be used to grip and turn the turkey. Then again, I never got around to trying it out.....