You could rescue the string and tie it all up again?
Alternatively, if the pieces are of roughly equal thickness you could cook it in separate bits until it develops a reasonable bark then wrap and see it through until 90C (ish). Then vent it for 30 minutes to bring the temp down...then re-wrap and rest.
I often have done something like the above and just arranged the meat so it ended up roughly the same thickness throughout. The only real issue is that rub stuck between pieces will tend to end up a bit grainy and blah. You can get around this be rearranging half way through though.
Allowing 8 hours is a good thing - always best to have too much time. Chances are with multiple smaller bits you'll finish cooking far in advance of that though

Just follow the directions above and once you re-wrap place it within a million towels, an oven at 50C or a coolbox (obviously without ice packs in

).