1) make two separate classes in ext_main() like so
t_class *jsmyclass = class_new("jsmyclass",yada yada);
jsmyclass->c_flags = CLASS_FLAG_POLYGLOT ;
t_class *myclass = class_new("myclass",yada,yada);
2) important: make sure that the mxo file is named jsmyclass,mxo. This seems to be key
3)add the appropriate file to jsextentions folder:
maxclasswrap("jsmyclass" , "myclass");
This should allow you to load myclass as a max object and a jsobject.