When fitting kadee's to Lima mk3's the #5 has to small a shank. I have found the the long shank kadees work best on the mk3's. Of the top of my head I think I used a kadee whisker coupler #146. You attach this to the chassis and not the bogie and it should work OK on tight curves. On another note regarding my UK stock I've started to fit a piece of wire to the locos as a coupler as the UK locos have a lot of detail parts on them and I hate detailing just one end and not the other. If a loco has the like's of snow ploughs supplied I want to see them fitted. If I get time tomorrow I post up a picture of my new Heljan WCR class 33 with the new coupler fitted.