The normal plunger stroke on the "2-11" style plunger tube is just over 4-1/2 inches. The stroke on the normal +bow plunger tube is 6-1/4 inches.
I came to the same conclusion you did when I was initially developing the 2-11. The extra volume meant that a longer stroke was excessive and I ended up cutting the spring shorter and shortening the stroke. I also got more predictable results using rubber washers than I did with o-rings.
However the tolerances on the 2-inch ID polycarbonate tube have gotten wider since then so I haven't been particularly pleased with that and it's something to be aware of. You WILL get a smooth surface and it will be perfectly round, but the ID is +- 0.050" for part number 8585K46. There's an alternate part number (9176T9) that doesn't list tolerances but I haven't ordered enough of it to evaluate it.
The 6-1/4" stroke 2-11 was a one-off thing for Gears. In a 1-to-1 comparison with a +bow plunger tube using a 10-inch barrel that one-off blaster was shooting an extra 10 or 15 feet. It obviously could use a much longer barrel, though I'm not sure what kind of pneumatic flow restriction limits may factor into performance.
Picking a larger plunger tube in order to obtain a shorter stroke length would be useful in certain design requirements. Say for instance wanting to ad a much stronger spring, then priming it with a 2-to-1 mechanical advantage gun tackle pulley. Or simply wanting a much shorter over-all blaster length.
A homemade Ultimator would be fucking awesome.
The little critters of nature, they don't know that they're ugly. That's very funny, a fly marrying a bumble bee. I told you I'd shoot, but you didn't believe me. Why didn't you believe me?