Hi Brushpopper,
Just cooked a Wagyu on my GMG DB yesterday. Trimmed and seasoned @ 2:00 am, Started the GMG at 3:30, and put it on @ 4am.
Seasoned rubbed it down with a good solid coat of Worcestershire as a binder, then liberally add salt pepper, garlic and Montreal steak seasoning.
Put on the GMG DB at 190 until IT of 165 (cooked fat side down first 5 hours, then fat side up for 3, then back to fat side down) Fat side down in pan as well.
Placed in covered alum pan with 1/8 cup Worcestershire, 2 cups water, 1/8 cup A1, 3 tablespoons salt, 1 teaspoon cumin and 1 teaspoon coriander. Added more Montreal steak seasoning.
Raised temp to 235 until IT of 195, removed and wrapped in foil for 1.5 hours
Total cook time was 12.5 hours, moist and tender!
Sliced and served at 6pm, Excellent!
Wish I took pics, but I didn't.
I have found that the GMG DB does much better at lower temps, more smoke and more stable (my experience). Been using mine for a touch over 4 years now. Made some pretty damm good food on it.