Jacky said:

Hi so if you have more than one champion in the fort which boost is selected for troops that is in fort... Is an average calculated? Thx) 

I have sent 3 defense champions to the fortress, if you pull all 3 out and send them one at a time, you will see your troops power increase per each sent. The higher level the 3 are the more your personal troops will increase. Same will work if you use the spy champions in the fortress.