As a suggestion (from an non air freight bod) If the vehicles are on pallets (adding height) you could take the wheels off them, rest them on flat rubber blocks/mats and secure the 'Cruisers to the pallets as a way to reduce the overall hight.
Just be sure to leave enough ground clearance to get a jack under them again to refit the wheels (and don't forget to pack the wheels and jacks whit them on the 'plane!)
JAS