If you like the GS, you will like the CT as well. I have only ridden R1200s, not 1150s, and if they are anything alike, you will find a similar position on CT. Your knees will be bent a tiny bit more, any upper body will be upright to the same degree.
The riding position will be the least of your worries, and you won't have that many worries to start with
For reference, check cycle-ergo.com