Can't help you with the specialty designed buckshot tubes. I have never used one personally or seen one in action. I have seen a lot of folks shoot buckshot through extra full turkey chokes, or just plain full chokes. In ever instance switching to a modified or improved cylinder improved the group.

I suspect the tighter chokes caused the pellets to bounce off each other, because the patterns were wide and had a lot of fliers.

Maybe some manufacturers have solved this problem. I would be interested to hear your results. Is the pattern simply high, or both high and more dispersed than you desire (or than advertised).