Karen: By cross braces, do you mean the 2X6's that go from a rafter on one side to a rafter on the other side? If so, these are called collar ties and are very important to keeping the front rafters from kicking out (or spreading) where they attach to the front ot the house. I don't think drilling a hole in the exposed collar ties will help much....you need to get outside air along the full back of the roof deck so that ideally, the temperature of the back of the roof deck is the same temperature as the exposed outdoor side of the roof. It never quite works out that way, but you can get it close by ensuring a good laminar flow of air from the soffit to the ridge vent. Seriously, I wish there were an easier way....but I haven't been able to think of one. Now if you are up to unconventional thinking, there is a school of though that says insulation should be blown into intrarafter spaces (cellulose preferably) with NO ventillation. This is done through a series of holes in the drywall or plaster ceiling. This approach might work in cold climates, but I just can't imagine it doing anything but harm in a hot climate.