Does the shape of a Sealed box matter as much as it would for a ported box?

I'd like to build a box that has a dip in the middle to better utilize my trunk space, I was just wondering if there are any issues with making a non-cube like sealed box for my dual 10's would be a bad idea?

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lx \__/ xl
l______ l

x = Sub
Thats a very very roough idea of what I had it mind (the dip in the middle is so I can fold the seats down and but a snowboard or 2 in). and it's obviously not to scale

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Inside my 96 Nissan Sentra:
Pioneer DEH-P8600MP
Pioneer Premier GM-X924 Amp Powering 2x JBL P632 midbass, w/ CerwinVega Tweeters, on Pioneer passive xovers
Pioneer GM-X922 Amp Powering a Pioneer Premier TS-W1041DVC sealed
Awaiting spring: Pioneer CD-635, Clif Design QX6500C, a 0g run and adding a Sony LS-1065g