I think it is possible to have 10 TRXs per cell.
3 TRXs just carry BCCH in the separated Channel Group number 0 without hopping and 7 TRXs can be shared between 3 sectors with SFH e.g. configuration can be 3+4+3.
Please note to this formula:
“number of frequencies in the HFS” >= 2*(number of TRXs in the CHGR)