woofer mounting depth

I am new here and would like to gain some knowledge from some experts like yourselves.

I just bought a pair of 07C108 10 inch/ 8 ohm kicker comp sub-woofers and these speakers require a mounting depth of 4 13/16 and the box I bought is sealed and has a mounting depth of 4.5 so barely not enough.  I fugured that I can get a pair of 10 inch spacers to make up the difference?  Would this actually work?  If my calculations are correct I would have a new mounting depth of 4.5 (4.5 is what the box has of mounting depth) plus 0.75 so would be 5.25. (the spacers are MDF and are 3/4 in size so converted 0.75 more of added depth mounting space).

Also the sealed box has 0.61 cu of space on each side so would be per sub-woofer and I know that these particular woofers require a minimum of 1.0 cu of airspace to perform correctly so if again there is 0.61 within each side and with spacers I would add (if I have a total of 5.25 minus the mounting space of each woofer which is 4 13/16 which would be 4.8125 converted) which equals 0.4375 extra and then add the 0.61 which equals 1.0475 cu of air space on each side then I should meet the required minimum air space needed for each sub-woofer correct.  Just making sure my system and calculations would work.

I am also pushing them with a ZX350.2 amplifier and since these sub-woofers are 8 ohm wiring them in parallel should bring them to a 4 ohm impedance and should push the subs at their prime at 350 watts @ 4 ohms easily correct.

Enclosure Specs:

Again just want to make sure this would work because I already have the amp and head unit installed.  I also already have the speakers and box just waiting for the spacers to come in and should be here by Wednesday.  Thank you so much!

I'm no geometry expert but I would say, no. I can only remember what my math teacher would tell me. "if it don't look right, check it again. IT don't look right.

It just don't look right to me. There is NO WAY you are going to get .39+ cuft more space using a spacer.

Looking at the calc. Assuming you use .5 mdf. 16x21x4.5 = 0.60764

You would have to raise the ENTIRE depth of that enclosure just to get to: 1.04167

sorry for type...(can't edit)

You would have to raise the entire mounting depth to 7" to get to 1.04167cuft.

I calculated the total for ech side.  For instance, if their is 4.5 cu on each side for mount space and then I add the 3/4 spacer or simply 0.75 converted so technically I would have 5.25 cu of mounting space for each side, right?   So if each 10 inch woofer (Kicker compteition 07 model) has a depth mount of 4 13/16 which would be 4.8125 cu (converted) right?  So if I have 5.25 cu of mount depth with spacers then minus the actual speaker mount depth then that would equal 0.4375 cu.  

If there is already going to be 0.61 cu of air space on each side I just added the extra 0.4375 cu to the 0.61 which gave me 1.0475 cu of air space.  I am not a math wizard just makes sense to me but no expert by all means.  Just want to know if the speakers that I have will mount and work correctly with what I got.  If not I have to purchase other subs, probably shallow mount for mount space.  Thank you for your time though.

You added the .4375 extra mounting depth to the box VOLUME. That's not correct.

I agree the spacer will work as far as mounting the subs, but there is no way you are at or above 1.0cuft. Not counting displacement of the driver even. 

and thus, an expert finally chimes in...thx j.reed. Like I've always said "there's no substitute for experience"