Hello Jeff!
The springarms and regular arms are not interchangeable in the mook jong trunk. This is due to the fact that the springarm has a different size hole in the back of the mook than in the front. Solid arms require the same size hole. Also, you cannot work the springarms for chi sao on the mook jong anyway. The arm positions are way off for chi sao. Today I am working on a doorway mounting system idea for both my springarms and mook jong. The springarm station would include the necessary position for chi sao rotation if you have two springarms, and also several height adjustment positions for the springarms, as well as a head height target for striking purposes. This mounting system could be put up and taken down in minutes! I haven't decided what this mounting method will cost, but should know by the end of the day.

Keep Blasting!
Sifu Lamar M. Davis II
Senior Instructor
Hardcore Jeet Kune Do
Sifu@HardcoreJKD.com
JKD@windstream.net
http://www.HardcoreJKD.com
Phone (205) 296-7070 (Incoming Only)
"Hit Hard, Hit Fast, Hit First - ALWAYS!"
"The REAL future of Jeet Kune Do belongs to US, the few, the proud, the HARDCORE! Now, what are we going to do with it?" _ Sifu Lamar M. Davis II