The instructions that come with the NexStar show a flap conversion, using two different methods. However, unless you were loading it up with who-knows-what equipment (60 size engine & floats perhaps) there is no way that it needs flaps -- probably not even with another pound or two of weight.

In my opinion, unless you were flying out of a very restricted area, flaps on a NexStar would be an interesting exercise to satisfy your curiosity, but would not really be worth the effort.