Run PX4 in your own gazebo model

I have created my own coaxial hexacopter Gazebo model: I want to be able to run PX4 for such configuration with the Gazebo simulator to close the loop?
Is this supported? How do I implement this? How do I link the hexacopter coaxial type of airframe to my model?

Hello Xun

Please check my answer in the topic below:

thanks for the reply @kangmin7! Still I am slightly confused.
In the PX4 User Guide it is stated that in order to create a custom airframe, you should include your config file in ROMFS/px4fmu_common/init.d.
However, after reading some discussions in here, I apparently have to include it in ROMFS/px4fmu_common/init.d-posix.
What is the difference?

I believe I added my files to init.d, not init.d-posix