Figure enclosure size, fab questions

[GearheadJim]

I have a '65 VW Notchback (not a bug, a sedan) and I'm working on my sound system installation. I am not going for all out performance, I just want to get the best sound out of the equipment I have. I will be mounting a pair of 6.5" coax in kick panels in front driven by a Fosgate 40w, a pair of 6.5" coax on the rear shelf driven by a Fosgate 40w, and a single 10" sub (space limitations) in the center on the rear shelf driven by a Fosgate 100w. I will be building a single fiberglass enclosure to cover the speakers and sub in the back. The enclosure will be sealed with individual, braced compartments for the sub and the speakers. The top will be made from 3/4" MDF to give the speakers a solid mounting surface.

I know that the size of the sub enclosure is critical but I don't know how to figure the size I need, any help?

Is the size as critical for the coax speaker enclosures or are there other factors that I need to consider for those?

I've read polyfil packing is beneficial. Is that for subs or regular speakers or both?

I purchased the kick panels for the front and am disappointed with what I have. About 1/8" thick fiberglass panels, no back just a front and sides with the basic correct contour, certainly not flush against the mounting surface. How conerned should I be about sealing these enclosures, do they need to be as airtight as a sub enclosure? I'm thinking about laminating a piece of 3/4" MDF on the front to give me a more solid mounting surface, good idea or overkill?

Specs:

2 Fosgate Punch 40s: 40w, 20w rms/channel, 4ohm

1 Fosgate Punch 100: 100w, 50w rms/channel, 4ohm

4 Apline 6.5" coax SPS16295: 30w rms, Response 40hz-25k, 4ohm

1 Apline 10" sub 6110: 120w max, 80w normal, Response 25-400hz, 4ohm

Thanks for all assistance.

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[Trixter 10+ year member]

To figure out the size of the enclosure you need for the sub, first figure out how much room you have to work with. If your going to put it in the rear shelf, measure how long and wide you can make the box. Then make the box however deep it has to be to get the right size. (L" x W" x D" / 1728 = cu') Find out the size that the manufacture says and then go from there. As far as the other speakers go, I don't think that it is that important to have an air tight seal.