Eardrum, one more thing to keep in mind. Barlowed long FL eyepieces might have problems with eye placement too, because the Barlow actually extends the eye relief. My 25mm GSO Ploessl is comfy on its own but real touchy in the Shorty Plus. In my limited experience, the barlow can also accentuate some of the design/build flaws of an eyepiece, like internal & stray light reflections.
Dave, I'd say no, 15 and 12mm are like 30 and 24mm in a scope with twice the FL. 30 & 24 don't sound like doubling up at all, do they?
