I am not sure that that you are referring to the correct pic numbers,
Pic 4 & 5 are just the bed I beams and the cross beams which will support the bed
Pic 8. is the double pulley which connects to the motor.
I think that you maybe referring to the following?
33. Welded a 30mm x 3.5mm nut I made inside a 8mm x 60mm pipe for the tool post holder. This becomes the sleeve for sliding the threaded MT3 holder in and out.
34. Tool post holder and sleeve.
38. Tool post handle with stainless tube handle sleeve.
39. Tool post locking nut.
37. Tool post mostly assembled
The planer idea that you have is a modification that I had in mind to do at a later date when time permits, using a mounted wood router on rails to mainly to take the excess wood from a log to make it cylindrical without having to use wood chisels to do that, using the VSD I can rotate an unbalanced log slowly and just use the router to remove the excess. Using the VSD, the slower I go the less torque I have, currently I have a 2 step range, High and Low and variable via VSD. so I am thinking about redoing the motor setup and moving the motor outside and putting in a multi step pulley system to vary the RPMs of the faceplate without loosing torque, and then using the VSD to fine tune the RPM's within the step range.
I don't think I can give you any ideas about the hydraulic tail post, with mine I have to physically push the entire back end post towards the log then clamp it down using bolts (Pic 39) to the middle of the bed, and then using the screw to push the live centre in to the log end. Once I have the live centre embedded into the log end I then just lock the nut on the thread and that keeps it all in place. If I understand your meaning, you could use the hydraulic ram to push the entire back end close to the log end and then just use the setup I used to screw the live centre into the log. For me using hydraulics is a lot of effort and cost to engineer something just to do what that I can do manually in about a minute, undo two bolts, slide post, clamp two bolts, adjust live centre, done.