I figured out how to disable hill assist on 2011 wrx. well i used an idea from a member on iwsti when i used Google. The car has two clutch sensors, one for safety switch on clutch other for cruise control/hill assist. The top of the two sensors is for hill assist and cruise. If you can figure a way to keep pin pushed down all the time hill assist hill never activate. Now i used a closed nut and adjusted sensor up a little to make room for nut. You need a 10 and 1.25 metric nut. now i have limited stores around me so i had to use a 10 and 1.50 closed nut and put a very small hex screw inside to push pin down and screw on slightly enough to stay on..
negative side effect is if using cruise control and hit clutch your engine will rev up. well if your smart and hit the break or cancel on cruise control you will be fine.