Your HB 2 is 6 channels CCPM. Using your existing 4-in-1, you need to setup CCPM on the tx. You probably also need to setup the pitch-throttle curve. You can use the mixer on the 4-in-1 but you should get better result if you turn down the mixer and do the mixing on your tx as well.

If you go seperate, you'll need to do all of the above unless you also use HH gyro then you can skip the mixer part.