I know the thread is probably void now, but I’ll throw out something real quick about the letus and the HPX300.
The letus works very well with our HPX300. The only major problem to watch out for here is if you are using the standard fujinon that came with the camera (Heaven forbid) in conjunction with the letus, there is a potential vignette problem. Which is why now we are no longer using the Fujinon standard and switched to our Canon with the letus.
You have to really push past the little box inside the letus system which I am assuming is the ground glass holder. Otherwise you will get a small vignette that is hard to see when you first set it up. So check your corners very carefully. I know it can work with the Fujinon but you really have to push past that box inside the letus, further than you would think you have to.
Remember I am solely speaking about the Standard Fujinon lens working with the letus system. I hope that made sense.