[Elecraft] K3: best roofing filter on RTTY

[Dick via Elecraft]

Hi Guys,
 
I'd appreciate your thoughts on the best roofing filter: 250hz  vs. 400hz, 
for RTTY contest conditions.
 
While I really like the K3 on RTTY, I believe improvement  can be made to 
my K3 RTTY reception.  Some contesters have  told me that they use the 250hz 
roofing filter exclusively when operating  RTTY contests.  Since the actual 
bandwidth of the 250hz roffer  filter is close to 370hz, and RTTY signals  
are typically about 370hz wide, then the 250hz roofer along with a 400  or 
500hz DSP setting should be close to ideal when maximum  selectivity is 
needed.  However, on both of  my K3's, when I switch from the 400hz roofer to the 
250hz roofer, the  RTTY signal is decoded a lot less often, about 25% less 
often.   It doesn't seem like the 400hz roofer should decode 25% more often 
than the  250hz roofer.  (but perhaps that's normal?)  
 
 
Perhaps there is a receiver setting change I  can make to the K3 that will 
improve RTTY decoding when using the 250hz  roofer?  I've tried various 
shift settings when the 250hz roofer  is engaged and sometimes it improves RTTY 
reception, but not  consistantly.   Perhaps there's a setting change I  can 
make to MMTTY?  
By the way, I'm using  both MMTTY and 2Tone software's for decoding RTTY, 
with basically the same  results when the 250hz roofer is engaged.  

 
Thanks in advance for your thoughts.
 
73,
Dick- K9OM