you need a very strong powerl control UL and DL, and a very very very good cell design (no overshoot, perfect tilt, not too much overlap, etc)
don’t forget to activate DTX ul and dl as well.
with only 12 frequencies, with SFH, you are limited to only 1 or 2 TRXs per cell !! More than this and you’ll certainly have a high call drop rate.
2 TRX : if your cell design is great
1 TRX : if you cell design is average
Your move to SFH is bold, it doesn’t look feasable at all (if you need more than 2 TRX/Cell). You’re certainly better off with BBH, at least you can control interferences.