I bought an HF 8 in april and tested it for the two weeks I had until the return period ended.
At the end of the two weeks I was hesitating. On the one hand, it offers a good bang for the buck, on the other hand, the comfort while flying was definitely an issue and the "ride height" was not optimal since I use a razer tartarus wich is mounted on a flip down table that is just above my left thigh and was now constantly resting on my leg.
I then decided to do something radical.
I took the HF 8 apart and stripped it down to just the shaker units and control box. I then cut holes in the foam of my seat cushions, integrated the shakers and wiring and made some modifications to the cushion covers to house the system.
Now I have regained the comfort of my rig with the advantage of having the shakers.
I know that the warranty may be an issue in case of a malfunction but for me there were really only two choices: sending it back or modding it to fit my rig.