I've done it both ways myself. In the LT-40 build thread I showed using a seperate piece of covering to cover the gap because it's usually a little bit easier for less experienced people to do than trying to do it with one piece of covering for the entire wing and control surface such as an aileron. I myself have covered many planes where I do it all in one piece, but it's not something that you're likely to get right the first time. That's why I didn't mention that method in the build thread, as it's targeted towards beginners in building and covering.

Either method works well and it's more of a personal choice on how you want to do it.

Ken