New the forum - Hi!. 
I have been using successfully old cakewalk with gigstudio 3 without any issues.  I am using sonar 5 now with giga and an having difficulty setting up midi trigger for the right port.  My loaded instrument selection in gigastudio  spans 3 ports each assigned 16 different instruments. 
Here is what happens 
Sonar: In/ from keyboard controller /out port 2 to giga
C B P is not behaving rationally.  For C  select 12 and the instrument on port 1 channel 12 plays. 
B shows no options
P is the puzzler.  Instead of providing the link to the three ports sonar signal replaces whatever I have loaded in channel 12 with the (port) I select - clearly not a port at all but rather sonar is assigning an instrument change in port 1. If I enter 82 I get a new instrument and giga only goes up to 8 ports.  so what's it reading?
Any suggestions would be much appreciated
thanks
ted
 

C B P meaning channel, bank, program, right?

yes correct.  in the instrument selection - I have managed to import roland jv1080 and everything shows up in its proper place.  there are no 'gigstudio' instruments however.

I wouldn't expect it to work as you're hoping.
I was using GS3 with Sonar 4 for a long time, close to 10 yrs., and the only way I ever did it was to build a Giga Studio performance for each song and manually name my midi tracks in Sonar.