structure prediction of two subunits using COTH/SPRING

Hi,

I have two fasta sequences of my protein i.e. alpha and beta subunits respectively.
I tried using SPRING AND COTH to predict the structure of functional protein but i am facing below problems.
1. The server is sending me message that it cant take sequences greater than 1000 residues.

I tried to trim and see if i can remove some residues which i presumed as not important. However the output secondary structure is not as expected. Can anyone tell me how to overcome this problem?