Exposed Wood Beam Ceiling repair - help needed
Your already have an insulation issuse. The real question is if you are going to have a cooling issuse. Hard to say with out seeing the home, the roof facing direction, tree cover, sized of units, windows, and other stuff I cann't think of right now. Sound like you are already done so go with it and try. To add a little more air flow tur nthe unit's fan selector to on instaed of auto if you are havving problems in that room. This will dirty your filters faster but may even out hte temps between rooms better.