I have a set of plans from reso outfitters for a six string squareneck reso. Thing is I think now I would like to build an 8 string. The obvious changes are longer headstock, wider neck and fretboard but what concerns me is do I need to build a thicker top, sides and rear? Or just top? or maybe leave them as per the plan?

Any suggestions about this project will be more than welcomed. Anything at all no matter how trivial.

Thanks.