Trying not to get too technical, but look at it this way. At your best sustained turn rate (meaning you can hold that turn indefinately without departing) in a plane, you are almost using exactly all the power being produced at the prop. If you use more power than is being produced, you eventually stall.
There are two types of drag using up your power, induced drag (drag from maneuvering), and parasitic drag (drag inherent in your airframe). When you deploy flaps, you are adding parasitic drag, but that by itself (by design) should not put you at a power deficet. As long as you're not inducing enough drag to put you at a power deficet, there's no problem
The thing to remember is that when you are not maneuvering, the extra parasitic drag from the flaps, will be robbing you of part of your excess power. Of course you'll always be wanting to be putting your excess power toward either speed or altitude to improve your energy state. So its a good idea to use flaps at any setting only as long as you need to.
If you get your 51 in a situation where it is slow enough to deploy more than 2 notches of flaps, adding more flaps will provide stability and lift. If the sitiation dictates you need the lift and stability, by all means do it. Just remember not to use them any longer than you have to.
