You might want to extract the OBJ geometry either manually (from the uncompressed PP2 file, using text editor), or by using third-party commercial utility software.  JCH Digital website has a tutorial on how to extract the OBJ, but I think there could be a semi-colon amiss somewhere in the instructions.  Put the OBJ under a suitable sub-folder under Geometries, and have the slimmed-down PP2 file refer to that external geometry. 

Eternal Hobbyist