Ok, I just calculated the relativ size of a JK2-Player in comparison to a Q3 one: You have to scale the objects from Q3 by 1.125 to get them to the exact same size in JK2. But beware: If you resize your old Q3-Levels you have to retexture it completely and relighten it, because the entinities are not portated exactly.
Hope this helps at lease some- elsewise I can say that I wanted to gather posts
