Definitely check your wattmeter and report if possible. I'm curious as my (same exact) power system gives me no problems and I fly at full throttle quite a bit!
I honestly think GP has the knowledge and is in the business of recommending and selling planes and power systems for a reason.... and NO they aren't my favorite! There may be an issue, so I would contact them after you find out what is causing your shutdowns. They will likely take care of you.
As stated, I have a WOT on the ground reading of 31 amps in with a 3s pack. The 35 amp esc supports that draw (and in the air it is getting airflow). This little plane can really turn and burn!