Take the Hydraulic Cylinder Base and bolt inside the 2x P11 Cylinder supports. Use a washer between the cylinder and both P11 parts as before.

Get someone to hold the cylinder base so the the very bottom edges of the P11 supports are aligned with the bottom edges of the P31 hinges and clamp them together (use 2x G-clamps) . leave enough clearance with the clamp to later weld on the seams.