@Boz - are they de - boned? If not, see if the butcher will do it for you (or do it yourself if you have time). But either way, see if the butcher will give you some of those elastic mesh bags for holding them together (better than twine). You will be able to get more on the grill and they will cook faster if de-boned. The mesh bags will allow you to slater the insides with tasty seasonings before bagging them up. Best guess - de-boned, 5 on the main, 3 on the upper. Bone in - probably 3 on the main and 2 on the upper. I wouldn't recommend using the lower grate, as those will cook faster than the rest, which means completely unloading the whole, very hot, grill to swap/rotate them mid-cook (or to just pull them off when done) - PITA!