Hello Bob.
with 36 hopping Freqs and reuse pattern of 1*3 with 12 TRX each you can have up to 8 TRXs per cell, i.e S888 configuration with MAIO settings as seen below;
Sector 1: 0,2,4,6,8 and 10
Sector 2: 1,3,5,7,9 and 11
Sector 3: 0,2,4,6,8 and 10
But challenge with 1*3 reuse pattern is;
1: All your site should be on grid and pattern
2: All your cells should have same azimuth.
I would like to recommend to you to use 1*1 reuse pattern for SFH implementation rather than 1*3 to due above constrains.