First of all, if you buy the HK or any other brand, please replace the plastic end piece with a wheel collar(ask me how I know).
Since you have to arm the esc, the throttle has to be off position. So, what that tells you is that you need 2 modes to get it to use reverse.
Mode 1 just handle forward motion.
Mode 2 When you flip switch to get reverse,the following conditions must exist. The engine speed needs to be the same and blade angle better be the same, or you will blow it up due to stress loads. Hence, center of throttle becomes 0 blade angle and some fixed rpm.
I always changed mode in air and throttle at half. Maybe you could play with the radio to set up mode two so it spins up the motor and jumps the blade angle to zero. That to me would be very dangerous start up.
If you go to Realflight, the sim is set up the same way. Mode 1 starts at 0 rpm and in mode 2 start at 5000 rpm and goes to 9000 to account for blade angle increases. The plane is the "Flatout with v pitch". Best I could do is go down slow, stop it nose down, too heavy to back up. The big trick to it is the airflow must be over all three control surfaces and ailerons must move + and - 80-85 degrees. His plane,setup cost an arm and a leg, so I ended it.
I like to design and fly unique planes.