90 degrees ok?

Would I run in to any phase or cancellation problems if I face my subs at a 90 degree angle to eachother about 24" apart. they will be about 5" from the back door and each will be angled 45 degrees to the back door. they are facing towards the back. any help would be great and I'll try to explain it better if noone can understand this.Pioneer DEH-P980BT, Zapco DCREF1000.4,Pioneer TS-C520PRS, Adire Extremis, MTX TA91002, TC Sounds TC-3000 15"

That looks like a good configuration to me.  They will both be angled at the same degree (to the sides), so each should arrive at your listening area at about the same time.  And they're close to the back which will allow both the front and rear waves to travel pretty close to concurrent.  Try them out before you put the final touches on the cabinet asthetics, if that is a possibility.  But, I'm guessing that once you make the shapes of the boxes the positions can't be changed...right?  One side flat to the car side, while the opposite side is angled at 45 degrees?  All in all, it seems that it should work, especially since they will be in separate enclosures.  You always have the benefit of reversing phase on one of them if you find it to sound better.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

The enclosures will be fiberglass and will use the storage bins on each side of the vehicle. each bin has about 1.4cuft each so i'll still need .8 cuft more per box. I'm replacing the flimsy fiberboard on the back door with .5" MDF sanded down and covered with suede. so it should get a nice reflection towards the front.Pioneer DEH-P980BT, Zapco DCREF1000.4,Pioneer TS-C520PRS, Adire Extremis, MTX TA91002, TC Sounds TC-3000 15"