I am considering a purchase of binoviewer to use with my 305/1500 collapsible SkyWatcher dob. I would like to use ADC for planetary viewing, hence I need at minimum a 2x barlow/f.extender. my question is: could the 2.6 GPC be placed before ADC, i.e. can additional 55mm of lightpath be introduced between the GPC and binoviewer (OTA -> 2.6 GPC -> ADC -> bino)? Focusing distance is not much of an issue, since mirror can easily be moved. I am more interested in understanding how GPC will behave - is it sort of telecentric or 2.6x effect with distance becomes 3x or more.