I got a Jensen MOD12-35 8ohm speaker for christmas. I have a 24" x 24" x 5/8" MDF panel that I originally cut and planned on using for a different project that I plan on using.

My question though is, is this speaker designed for open back cabinets?

I used WinISD to model an enclosure, and with its extremely high QTS, it has a large peak around resonance in a sealed enclosure

Wouldn't an open backed design be even worse, as the back would be functioning somewhat like a port?

Are there any good resources on guitar cabinet building and theory? All of the enclosures I have built in the past have been for HIFI speakers, which is a bit of a different approach than a guitar speaker.

Washburn X50PRO FE (GuitarHeads active bridge pickup)
Dean Vendetta XM
Jet City JCA20H head, w Eminence Texas Heat 12"
Danelectro Transparent Overdrive
Ibanez TS7
DigiTech RP-255
Behringer VD1 (Big Muff PI clone)
Personally, I'd just test it out by ear with open back, closed back, 1/2, 3/4, 2/3 ect. to see which sounds best. It depends on the amp and speaker combination. If you're getting too much bass then open it up a bit until you find what you like.
Warning: The above post may contain lethal levels of radiation, sharp objects and sexiness.
Proceed with extreme caution!