In October, we took the boat from MK to FW for HDDR, so the boat was very crowded, people standing everywhere. We found that the manual WC was very hard to maneuver onto the boat (there's a turn) and the fact that they pack people on like sardines for HDDR made it a very uncomfortable ride. One wave, and someone's in your lap. Getting off the boat, we tried to wait until everyone else was off, but the chair had gotten turned in the path somehow so that people were literally climbing over us to get off the boat. (and we were stuck, couldn't move until the crowd thinnned)
I can't imagine that boat with an ECV. My advice is, if you're going over for HDDR, go as early as possible in the hope of a less crowded boat.
Shelley