I also own one of these fine stick and rudder aircraft, a 1940 J4A model. Definitely not a speed demon but cruises around 75 mph on an A65. Have been thinking about dropping an C85 on it just to improve the TO and landing but then that's more money to stick in the J4 that I really need to finish my 180 project.
The J4 interior compared to my prewar Chief is defined bigger and overall the J4 stands a little taller. Both great airplanes though and cheap to fly/maintain.