A tip or two to improve your chicken.
Spatchcock or butterflied chicken is about the poorest way to cook a chicken. You cut the chicken open and in your case, put it on the grill skin side up so all the juices with cook out of the chicken as there is nothing to stop the juice from running out of the meat. The heat from the fire will bring all the juice from the meat to the surface and it will just run out of the meat.
Ok, so if you must do it this way, place the chicken on the cooking grate skin side DOWN! Use the wonderful skin to block all the moisture from running out of the chicken when the heat pulls the juice to the surface of the meat. Do not turn it over for any reason and complete your cook in this manner. Even when you take it off when done, be very careful to keep it skin side down while it cools to allow all the moisture on the surface to return to the meat.
Skin side down will usually result in better skin on your finished chicken especially if you are using a good chicken grilling temperature of at least 300 degrees measured at the surface of the cooking grid.
I think you can see the puddles of juice on this butterflied chicken and this is constantly oozing out of your meat during your cook if you are cooking skin side up. Imagine, if you could keep all this wonderful flavor and moisture inside your finished chicken?