Replace the tanks valve with an unregulated one or try to up the regulator setting. The only other option would be to sell it and buy an unregulated tank instead. How small is this tank? If its one of those little 90 cu in tanks you wont get many fills even with it unregulated using it on a 250 bar fill pcp. If thats the case you would be better off selling the little tank and getting at least a 75 cu ft tank.