3 15 JL's and box size issue

I have 3 15" JLs that i'm going to put in the hatch area of my PT Cruiser. I have 3 15" W3's, and 3 Kenwood 1,000 amps powering each sub. The recomended sealed enclosure according to JL is 1.50-2.75 cu.ft. for each sub. Now, being I am putting 3 15"s in my car.. i'm not too sure if i'm going to reach that. With that being said, should I chamber off each of the subs, or should I just leave it as one big box?.

One other question, I know this should be in the fiberglass forum but I don't feel like posting another thread lol. These 15"s are going into a fiberglass enclosure. The back, bottom, and sides will be 3/4 mdf, and the front will be fiberglass and I plan on laying a minimum of about 7-8 layers of mat. Should I fiberglass the inside of the box rather then the outside?. I heard it's easier to glass the inside, because sanding down resin'd fleece is much easier then fiberglass. After the box is complete, am I supposed to spray a sound deadner over the fiberglass on the inside?.. or is that not nessesary?

You must chamber off each sub, make sure to heavily brace each enclosure as well. Yes, glass the inside of the box, it does make a much easier sanding job. Sound deadener works great on the inside of a sub box, but I personally would have it Rhino lined (truck boxliner spray on material). This will totally seal the box for 100% guarantee of no air leaks.

Are you sold on the idea of the 3 amps, one for each sub or can we talk you out of it and into a better option?

Thanks for the responses guys.

After all the trouble i've went through in getting a 3rd sub and amp, I really do want to keep a amp to each sub. At least now I know regardless of size, I need to chamber the box into 3 sections.

Thanks!!