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Steve,
The point of 2" eyepieces is that on a long focal ratio scope such as a refractor, an f/10 SCT or f/15 Mak it takes a very long focal length eyepiece to come close to the maximum exit pupil. For example, an f/7 refractor takes a 40mm eyepiece to produce a 6mm exit pupil. On an f/10 SCT, 60mm. On an f/15 Mak, 90mm.
The point here is that the longest useful eyepieces in a 2" barrel are around 40-50mm focal length. These are big, heavy lumps of glass.
2" eyepieces are simply not really relevant to fast dobs - for the simpe reason that you can reach the maximum exit pupil around 6mm using 1.25" eyepieces around 20-30mm focal length depending on your scope. If you put one of these big long focal length eyepieces into a fast dob, the result is an exit pupil larger than the iris in your eye. The result is that a significant portion of the light from your scope does not enter your eye, and you may as well use a rather smaller aperture.
I see a lot of angst on cloudynights where people try to stuff big 2" eyepieces into a big dob in the hope of ever wider fields, a rather better solution is to use a smaller refractor.
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