I think you might check out the shen hao hzx4x5, although it has more movements than you want, but that should be easy to fix. Not sure what you mean by triple extension, you got me there! But shen hao will do some custom stuff if you wish, as will argentum, probably. I also am not sure about the independent locking, you might need to do some of your own minor engineering with these light field cameras. I mean, you could easily remove whatever movements you don't want and add extra locks.