The MK1 is the first version published as PathFinder PRO-file, in Flying Models. Kenn Smith, now deceased, released a run of 200 kits of the MK1 from his company, Smith Models around 1995. The MK1 had a longer wingspan than the MKll and used a wide, notched, single spar that allowed a twist and lock method for installing the ribs. It did not have a sheeted leading edge but instead, used half ribs.
Due to the feeling that the spar may be a possible liability Gordan had me make a few changes to the plans that are used on the Brodak MKll version. Basically, he shortened the wing, and went to a C tube, leading-edge. This made the wing stronger, and less liable to flexing.
If you go to the vendors' corner, here on Stunt Hangar, and look under CadClassics, there's a pretty complete history about the Pathfinder series that may be of interest.
I'm attaching a picture of an MKll converted to an electric Pathfinder Twin, built by modifying an ARF
John Miller