"Great Weapon Master should give you the choice of taking the -5/+10, or doing a straight up attack."
Having anything minus completely defeats the name of "Grand Master" of that particular skill. That one is the most ridiculous feature, rule, feat description ive ever seen. I dont care if its by the book. The Book is wrong.
On the right side of the interface bar, there is a little circle that you can click to enable or disable weapon master power attack. It's the same area where you can turn off taking attacks of opportunity, etc