With that receiver/stabilizer HK recommends to set the switch to elevons and leave the transmitter in normal mode.
That is the way I have a 100 mph Stryker setup. It flys like it is on a tight wire in the sky.
Don't turn up the gain past the 50% mark or your plane might start an aileron wiggle that is extremely fast, luckily I was able to cut power, before the plane came apart.
I have over 800 watts available so I don't know how fast it will go. I used about 500 to go 100 mph.
Please let us know how your plane flew, I am looking at the Radjet, to see how fast I can push a flying wing.