You need to have lvl 6 Rim Blow => unlock high guard attribute: rim blow specialty.
You need to have lvl 6 Umbo Blow => unlock high guard attribute: umbo blow specialty.
Note: **+**100% is the same as 200%.
+150% (or 250%) at level 1,
and +20% for lvl2, +20% for lvl3, +20% for lvl 4, +20% for lvl5.
So max (250% + 80%) = 320% damage (or +220% damage) for level 5.
You need to have High Guard buff activated to get bonus damage, so need lvl 1 High Guard.