Hi - I used to sell these many years ago.
The TT is designed to work with a clamp and a washer under the record.
Something in the back of my mind says that on the early ones the spindle was threaded on the inside, not the outside as per normal, so getting a clamp will be difficult. A reflex clamp such as the SOTA should work.
With regard to setting the arm up - you leave the trough out and align the cartridge as per normal.
Set the tracking weight and level the arm.
Then you move the trough into position and lower the arm onto the record.
You then adjust the height of the paddle in the trough so that it doesn't touch the bottom of the trough as it transverses the record.
You can reduce dampening by decreasing the depth that the paddle is sitting in the trough.
The vertical arm bearings on the Rock tonearm used to stick. There is a fix which involved removing the arm, gripping the 2 vertical bearing points on the side of the armtube/bearing housing, and giving it a good shake. The arm inside is held by friction only, and occasionally it drops and sticks.
The arm works very well with MM's, less so with moving coils.
A lot of owners used to replace the original arm with Rega RB300's, there was an optional paddle for using alternate arms.
If you have the Merlin power supply it has trim pots inside for setting the voltages accurately. I have long thrown away the instructions for this, but Max Townsend, the designer may be able to help. From hazy memory voltage coming out the back should be 70volts.