I have not run any laps in GNS mod, but for cup I used Volker Hackman's Watkins Glen setup, and manipulated the gearing (1st and 2nd) to give more power coming out of the slow corners. A good Infineon setup would also work (you would need to modify 3rd and 4th gear to get more speed as the straights are much longer in Montreal.

In summary a good road course setup will work on other road courses as long as you play with the gearing a little...

Cheers

Brad