YIKES! STOP SHOUTING! (Caps are impossible to read!)
The best time to design-in building efficiency and moisture control is BEFORE the framing is done and you're slapping up the stucco. With a stucco exterior and an arctic-cool interior you'd have done well to put an inch or two of closed-cell foam on the exterior (not half-pound Icycene) to both air seal and protect the sheathing & studs or wallboard facer against condensation and mold in the walls. Closed cell foam is about R6/ inch, and at 1 inch it's a ~1-1.3perm vapor retarder, at 2" it's reliably under 1 perm and R12. But at a buck a foot per inch it adds up. Even at 1 inch of exterior closed cell it would be sufficiently vapor retardent that the AC would keep up with the moisture drives from the exterior, an any cheap stuff you stuffed in as cavity fill would be more than enough R, and cost-effective, but it would have to be either un-faced batts- no kraft or foil facers, or blown/sprayed fiber. Wet-spray cellulose is usually cheaper than Icynene, and about the same or slightly higher R, and has a bit of thermal mass (it's roughly the same as going with 5/8"or 3/4" wallboard instead of 1/2"
If the mechanicals & ducts are in the attic rather than inside of the insulation and pressure boundary the battle is half-lost and we're playing make-up, which can be expensive. If you're talking about putting Icycene on the roof deck (presumably because you DO have the ducts etc in the attic), it's cheaper and more effective to put R10-R20 as rigid foam above the roof deck (3" roofing-iso is ~ R20, and runs $50-55 for a 4x8 sheet, 3" EPS is R12, and about half the cost), and do the interior as blown cellulose on the attic floor- up to 10" or so is pretty cheap. (But I suppose we're late to the party on that.) That way you all but eliminate the thermal bridging of the truss/rafters. And it puts the ducts at least partway inside the thermal envelope, lowering the insulation requirements on the ducts. Air-sealing the roof deck can be done with spot-foaming the seams, it' doesn't need a full-foam overcoat, but air sealing is critical if the ducts are in the attic.
At low or no additional cost, going with CRRC rated "cool roof" shingles on the roof is more effective (and more cost-effective) than interior radiant barrier (but I'm guessing we're late to the party on that one too.) See:http://www.coolroofs.org/
Tell us more about the state of the project here (in a more favorable font, please, even if it's all lower-case.)
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