I've done a small spatchcock turkey the past couple Thanksgiving and really like it. Usually do chicken once every 2 weeks. Rarely do roti chicken anymore as i can get much crispier and falling of the bone juicy chicken. The process and setup i use for turkey is very similar to photos below.
Using a stacker, top of poortex is about 8" below the grate. The chicken is placed on a rack atop a very thick shallow ss pan. Rub for the bird with coarse salt/ pepper. Slices of lemon with s/p goes inside the skin.
Very crispy skin practically bubbling out of the bird and at the same time falling-off-the bone juicy. Obviously you can't achieve that tenderness with a turkey.
JV