[ICOM] Use a RTTY filter in SSB on IC751a?

[JimR]

I use a soundcard with MTTY to operate RTTY on my IC751a (radio set to 
SSB mode).  In a RTTY contest such as this weekend, the QRM is 
unbearable, and I'd dearly love to use a filter such as the FL-52A to 
kill off the adjacent channels before the AGC squashes the quieter 
signal that I am trying to pull out.

A buddy suggests that I could plug the FL-52A 500 Hz RTTY filter into 
the SSB socket to fake out the radio.  From the manual, I doubt that 
this would work.  Can anybody on this list clarify?  If not, what do you 
suggest to implement a tighter filter for SSB-soundcard RTTY?

Thanks and 73,

Jim