Ok. Just to report- I have decided, at least thus far, locking through with a single screw trawler, even without a bow thruster, is very easy and not hard at all. We went through 2 locks the last 2 days each dropping about 50' or so. Total cakewalk! I feel like I am getting more and more comfortable handling this little old trawler and going through the locks really was very easy...total non event!
It is great to get your feet wet locking down... the boat tends to ride out away from the wall on a down lock... not so on a up lock.* Last summer we got really good at locking on our trip up and down the Columbia and Snake rivers.. We found that with a single bollard can the lines needed to be pretty tight of the boat ended up with either the square point of the transom or the bow wanting to drag up the wall. We used 6- 30" orange commercial round fenders on Volunteer and we ended up replacing four because of small pin hole leaks.
The walls of the locks there are about as smooth as macadam.* I wanted to make up a set of tire fenders for the trip but never got to it... with the new boat we are going to do the CC. fender boards... tires look tacky hanging off a Sea Ray. We also tried to use a combo of bow thruster and prop wash to lessen the up lock drag to no avail.. but some of the locks lift over 100' and I think the lockmasters enjoy watching us fight the current.* With the winds* ( we had 45 kts one day ) on the Columbia sometimes just getting into the 85' X 600' X 120' deep lock chamber is a chore in itself. Going down we cranked up the tunes, danced on the flybridge, drank beer, and never even looked at the lines... the boat would stay a couple feet off the wall.
The last thought is we always ran our lines from the boat to the bollard back to the boat as our safety in the event of a hanging bollard.