How to select appropriate symmetry numbers?

Here is an example how to choose appropriate symmetry numbers. We focus on ¹H  chemical shift anisotropy (CSA) recoupling at ultrafast MAS. The sequence should be  satisfy the following conditions:

1. (1) ¹H CSA is recoupled at 1^st order.
2. (2) ¹H-¹H dipolar and ¹H isotropic chemical shift are decoupled.
3. (3) RF field amplitude is kept below 200 kHz at a MAS rate of 70 kHz.
4. (4) a large scaling factor is desired.
5. (5) the effect of RF field inhomogeneity is minimized.

Reference

M.K. Pandey, M. Malon, A. Ramamoorthy, Y. Nishiyama, J. Magn. Reson. 250 (2015) 45-54.