You will need some kind of peep sight to center your eye in the focuser to be sure the secondary is centered relative to the focuser. The 2 sites I linked before have some info on this. A film cannister with a tiny hole in its center will get you close, and a machined tube will get you closer. Astrosystems mention this in your instructions at the point of rotationally centering the secondary.
Sounds like you need a focuser with a longer draw tube and/or with more travel. So long as the eyepiece is centered and not going to fall out then it should not be a big deal. You can get extensions for eyepieces which screw into the filter threads to increase the tube of the eyepiece. My own GSO scope has the opposite problem. I do not have enough inward travel on the focuser for barlows and cameras. I will need a VERY slim focuser with long travel or something like this to correct for the problem-
http://www.siebertoptics.com/Camera%...0Adapters.html
Apparently I can also shorten my trusses??? Need to look into that.
Mark.