Yea I have the same problem in real shallow water where it can be difficult to steer with the rudder pointing straight back, but it's actually not a problem, it's an advantage. When coming into the harbor I sometimes sail over a shallow sandbar at the harbor entrance (about 5"- 6" deep). What I do is release the lock on the rudder, and the centerboard, and park my pedals against the hull, or pull the mirage drive then sail right over the shallows. With the rudder pointing straight back it is much harder to steer, as soon as I get back in deeper water I pull the rudder back down and everything is ok. I expect because the rudder has so much turning surface it is much more difficult to steer, this is not a problem, it's actually a pretty cool design feature being able to sail through 6 inches of water. As soon as the water gets deep enough I lock the rudder back down and off I go without missing a beat. You don't see any other sailers doing that, and they all look at me funny, but hey it works, it saves me having to go way around following the channel markers (about 15-20 minutes saved). Most boats can only go in 10 percent of the Florida intercoastal waterways (where the channels are), I can use 95 percent, sailing anywhere I desire, low tide, high tide, mangroves, I don't care, I like that. There are many pristine and beautiful areas that I can go where only kayakers dare, but way faster LOL.
Hope this helps