Stacking Question - Leia and Chagrian Merc Commander

I searched and did find a thread with this combo mentioned. However, I did not see any comments regarding it. Does Leia's CE stack with the Chagrian's Bonus to critical hits? Example:

Leia activates and has Luke CotF use her CE. On this immediate attack, Luke decides to Use the Force. Does Luke gain an extra +10 from Leia's CE and another +20 from the Chagrian's CE?

If I understanding Stacking rules correctly, I am guessing no (since they are straight bonuses).
Your assumption would be correct. As they are both direct bonuses, they do not stack.
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so would he get the +20 to damage instead of the 10 that leia gives
Yes, you always take a mix of the better of the 2. So he would get +4atk and +20dam.