Parbuckling is pretty easy and you could certainly get a 30' plate up to where it needs to be. Bents are all raised and braced. Put planks across tie beams to stand on. Run a separate rope through the tenon hole on the top of each post. Tie a knot. The rope is fixed at the top now, runs down under the plate, and back up to 2-3 people on each rope. Everyone pulls, the plate rolls up the rope, you sit it on the tenon shoulder, untie ropes and all is good. I have some pictures but no time to post them.
Brad