Some key points and changes for the future, based on 1.4kg \ 3.2 lbs:-
Cook to a temp and probe for tenderness, rather than be time focused.
Very spicey, (had used BBQ pit boys rub recipie) could reduce or even remove rub spices in future
Ensure snake is more tightly packed, coal could be reduced to half circle for a 6-7 cook
Hickory soaked only need 2 pieces in the first qtr
Mop every hour
Reduce initial cook time to 4 hrs (from 5 1/2 ), as the meat was slightly overcooked
Reduce BBQ temp 230 - 250 max
If it stalls for more than 1 hr, foil at 160-170f
Stop when meat temp reaches 195f and leave to rest at least 1hr
The next attempt will be a 3 kg \ 3.6 lb flat this weekend and, if the delivery arrives, using a Slow'n Sear.