You can use your true bar to measure base bevel. Place it flat on the ski as if checking for flatness. You should see daylight over the edges. This daylight will look like a triangle of light above the edges. This represents the base bevel. Now slowly lift up one side of the true bar. When the triangle of light disappears your true bar is the same angle as the base edge. Note how high you lifted the other end of the straight edge. A rise of 1 mm of the true bar 50 mm from the edge represents an angle of 1.14 degrees.
FWIW, I found when I first got on fat rockered skis they threw me in the back seat especially in powder and crud. I have learned that you want to ski a 5-point ski such as the Q98 in many conditions as if it were a SL ski. I'm on Bent Chettlers (123mm) and ZAGs (91mm) 5-point skis and they demand a forward COM or they will fly away from you like they don't want you on board.
I would examine technique after ruling out any obvious defects in tune. I find the recommended traditinal (vs center mount) mount points are a good starting place for most skis.