Where I ended up was :
i) take a bow rope to one of the numerous bollards, to control sideways movement a bit (and in particular to stop you crashing into the other wall)
ii) open the gate paddle on the same side as the boat.
As you say, these paddles are large and strong, and one will fill the lock pretty qucikly. Opening one paddle makes especially good sense if you are single handed, or have only one crew, as (on the guillotine locks) there is no way to cross over the top gates. [by the time you walk around the bottom end of the lock it will be nearly full anyway.]