Yeah you can still use the 3 in 1 board with a HH gyro. You have to bypass it though with an external tail motor ESC. Electrifly C 12. You also need some soldering stuff as well.

I picked up a cheap $44 Telebee HH gyro and it works great.

If you go to Helimax-rc.com and click on the AXE CPV3 and you can look at the owners manual on their site and it gives detailed instructions on how to install a Tail ESC and the HH gyro. The only thing is they want you to use a $129 GY240 gyro, yeah right. I'm freakin cheap so I used the Telebee LOL. Does the same thing. The only thing I needed was a Servo Extension wire for the ESC to the HH gyro. If I knew I needed one I would have bought one, so I ended up having to make one while I had the soldering stuff out.

It flies so much better with the HH gyro. Without the Gyro it was nearly impossible for me to do forward flight manuvers because I was always manually having to keep the tail straight. With the Gyro you can set your gain and trim it to where the tail stays straight and it'll stay consistently straight throughout your flight.

Without the Gyro I noticed the tail trim would change drasticly through out the flight. When the battery got below halfway it constantly got out of wack.