Lots of people will lay small bags of ice over the breast meat to get it colder than the rest of the turkey before cooking. I'd think it helps the bird (whatever the size) cook more even. Others will foil the breast meat for an unspecified amount of time during the cook.
I don't see a problem with the larger bird. If it fits in the egg, it should cook up nicely.
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)