Alright so my 1986 Celebrity 210V is getting lots of works done on her... I've ripped out all the rotten interior pieces and I have to re-build my engine cover and back seats. How much room do I need to leave from the top of flame arrestor/carb to the bottom of the cover? I was thinking about 3"-4" between them.. Is this enough? I was planning on building it out of marine plywood and covering with upholstery. Any ideas of sound dampening materials? Any other suggestions on this project? Thanks in advance....