[ccp4bb] Problem in molecular replacement

[dusky dew]

DEAR ALL
I am trying to solve the structure of a protein DNA complex with molecular
replacement. The resolution in about 2.5 angstrom.  The spacegroup is P21.
The search model has about 50% identity and is a dimer of a dimer. The
problem is the unit cell is huge and so the number of molecules in asu
becomes 4 or 3. I am not finding any solution with phaser/molrep.
Please suggest.
Thanks
Yang zhang