dhardesthard -
Due to high cost of fuel in Georgetown it is standard policy to tanker enough fuel to return to home base without refuelling. I doubt that this was a case of not enough fuel. However it may have made a difference if the A/C had only uplifted enough fuel in POS for a one way trip. Just speculating.
With 154 passengers the amount of payload capacity available for 'tankering' fuel, before reaching max landing weight, is very limited.
I'd estimate the amount of fuel they could 'tanker/ferry' before reaching max landing weight is probably less than 6,000 lbs. Six thousand pounds is maybe 200'/65 meters)(?) extra landing roll.