Good Show !!!
You might be able to squeak out a 6 hour hold..........what needs to happen is for the piece
to stay above 140, if it drops below that, then there's a limited window reguarding food safety.......
It's also a better serving temp up around 160~170 to start, when you 1st place it out that is.....
If I hold a long time, I'll open the foil up partially, crack the piece open in several places (a butt crack, so to speak...) add a 50/50 mix of apple juice / apple cider vinegar, Mojo marinade also works well for this, or a small amount of the same rub used dissoved in water...........
Heat the liquid a bit & splash it down into the piece & heat it back up a short while on grill or in oven.................
You can also shread it out entirely & add the above liquids in a small amount & heat that way, just before serving, IF the temp seems lower than you'd like............