I usually replace the rope seals with the neoprene lip seals. I put them in a little off center so the seals seam doesn't line up with the main cap seam. You won't have to drop the crank that way, I just turn the crank while pushing the seal into place, letting the crank pull it into it's groove.
If you're dead set on using a rope, pre-form the block side using the main cap. Stuff it into the cap until it takes the shape. Also, buy a couple of extras so when you trash one you still have parts on hand,
Scott