Twin rudders good or bad ?

A kickup, under belly rudder is possible and I have several on different boats I own and have designed several as well. They add no more complexity then a transom hung arrangement, though certainly more convolution with the engineering. Unless the boat will need to tweak out the last 10th of a knot in a race, there's really no advantage to twins. Redundancy be damned, frankly, you're just adding weight, complexity and complication to the butt of your boat. A single canting rudder might be a better idea on a narrow stern sharpie. I still think this is way over the top, considering the performance envelop enhancement you'll receive, but some just have to have the latest and greatest fad. Lots of wings got stuck on late 80's fins as a similar result of fad following. Don't get me wrong, on some designs, a twin setup is a must, but on the remaining 95%, just a fad driven contrivance.

 

You dont have to worry. The Macgregor 26 has been using them for years, and the rudders are hung under the stern, but can pivot up for motoring.

The performance of your boat will not suffer unduly, but I can confirm from personal experience that the motor/twin rudder concept works well.

Theoretically, two rudders is more drag, but this wont be noticeable unless in very light airs, when you can raise one rudder anyway.

Unless you are a mad racer, the whole issue is pretty academic, and not going to cause problems.