I picked up a project mando that had a cracked top. I replaced the top and made it an F2 style. It worked out pretty well and I currently have another project waiting in the wings. It's a Kentucky KM675. I removed the damaged top off of it and I have a rough carved replacement top to put on. I think I will do another F2/4 style with this one. I would suggest you consider the possibility of replacing the top. You might first try to x-brace the current top to see if this helps stabilize it.
Cabin Fever String Band, National Pike Pickers