Brian, Welcome to the build. Man you can cover this thing any way you want. I chose Koverall because you can hide the seams and overlaps. When finished it looks like one piece. If you are comfortable using 21 st century cloth then by all means use it. As for engine choice I am sure that any of the ABC schnurl ported 60's will work. The plane builds pretty light so you should be ok. You dont' have much choice about flaps, it comes with them. You would have to modify the wing build to leave them out. All the parts and hardware for their installation comes in the box so its not like you have to do extra work. Follow the plans and they are easy.
Mine has not been flown. It is still awaiting primer and paint. You can contact ken @ mosqitobiteplanes.com and he will be happy to give you all the info you need about the flying charateristics. From what I have seen it flys great.

I hope you enjoy your build as much as I have. Post your progress from time to time and send a picture or two, I'm sure the readers of this thread would like to see them too.