Yes, I cinch it up tight -- that's the way it's designed. I believe the system has some additional "give" built in. Also, the rudder pin is engineered to fail if necessary to save the rest of the assembly. A spare pin costs about $3.50.
Adventure Islands break their pins occasionally due to high sailing speed and high rudder pressures so they come with spare pins as original equipment. I believe all the 2009 (and some 2008) 8" hatches incorporate a slot for pin storage. Here's what it looks like (with spare pin in):

So cinch your rudder down firmly, carry a spare pin, make sure you know how to push the old pin out and drop the new one in on the water (just in case) and your rudder should behave very well. I think it's very unlikely that you'll break a pin, but it's good to be prepared.

PS If you customize the bottom of your rudder, a little radius (about the size of a quarter or so) on the leading edge is good to have.