I haven't had an opportunity to review the GA8 loading information but suspect that there ought not to be anything terribly unusual about it as the aircraft is very conventional.
About the only thing I can bring to mind as a possibility is that the engineer who was heavily involved in the early design development (Colin N) was ex-Nomad and the Nomad AFM had an unusual (but entirely fine) trimsheet entry argument design (the name of the chap who came up with it just eludes my recall at the moment although I can picture him quite clearly - while it is a cute solution it is, in my view, inferior to the standard way of doing things).
How about you post some graphic scans from the GA8 documentation and we can offer comment for the interest of the readership. Along the way I'm sure that your main question can be answered very quickly and simply.
Warning - please be very careful pinching someone else's computer based loading system (or, for that matter, paper based loading system) unless you have the capability to review, test and determine that it is applicable to your aeroplane .. a real trap for young players ... one of the reasons that most jurisdictions require an appropriate person to approve loading systems.