@CharliefromLIDon't think too many people are as daffy as me to then set the pan down in.......it works pretty good, I put celery stalks across the bottom of the pan to keep it from cooking / sticking to the pan......
The bottom of the piece doesn't get a crispy skin like the rest, but not soggy, as there's liquid in the pan (I fill part way w/ chicken stock & spices).......that does keep the bird generally real moist though........
Other possible downsides are being careful to not singe the areas closest to the coals & maybe oversmoking by a bit because it's right there by the fuel.......done it this way for years so it seems easy, but up on the rack works fine too.....
On the regular cooking grate, it limits the size by a bit, but you do get great heat flow that way......some folks will cook breast down for a time & flip for the remainder, claiming it ends up cooking thru more even that way & that seems to make sense......
Here's also some ideas from people last year......
http://weberkettleclub.com/forums/grilling-bbqing/wkc-turkey-noob-thread/I'll bump this up for everyone as some god stuff happens when folks chime in........