If you are using Common BCCH with 1800 as non-BCCH band,you are not defining SDCCH on 1800 TRX,do you??
In that case all RTSL’s can be configured as TCHD.
Well,if you are using Dual band N/w(BCCH in both 1800 & 900),the same rule of 900 applies for 1800 too.
FRL & FRU is the most primitive one to do so.
Lastly,your HR% should be 20-30% ideally.