Transpiration Bags, One More Time.

Yes, I have already read all 27,436 posts here. I have also read everything else I could find. The "experts" always seem say use "LARGE" clear bags. What if you are in a semi-arid zone and only have small trees and bushes to choose from? It would seem that a larger number of smaller bags, say 15 to 30 gal. would do a better job. Please share your field experience in this regard.
Thanks,
AL