We had the same experience with sheet metal presses where the base, two sides and crown were connected with large diameter tie rods 6-7m long. For the early presses we had to heat up the rods to expand then flog the nuts up. Later presses used hydraulic nuts, much easier!
I don't think my Copperslip is the real stuff which is why I'm going to use the Mintex Ceratec.
Iain