modeling a protein with residue number higher than 2,600

I want to model a hexameric protein which has 425 aa long monomeric units. Is it possible to do it offline. This will have various known homologous templates. It will not be a kind of threading instead a homologous modeling. I have ITasser installed on my system and it is showing error :
1. make seq.txt and rmsinp
error: the sequence length is not in the range [10, 1500]
Thank you in advance.