I recently purchased a 10mm Ethos and found difficulty focusing in my GSO 12". If I used it in a 1.25" adapter i couldn't rack it in enough, if it used the 2" barrell it couldn't be racked out enough and I had to sit it out a little. I solved initially by winding in all my collimation screws so moving the primary away from the focuser so I could get focus.
Eventually ended up buying a Televue High Hat adapter (see here
http://www.televue.com/engine/TV3_pa...=23&Tab=_equil ) that solved the prob. The only other solution was getting par focalising rings.