RE: G90 mounting??
I have a similar sized and shaped gyro and I mounted mine on the right side of the frame instead of on top. I started out with mine on top but too many vibrations went to my gyro, so that's why I moved it. I do see that a lot of people have theirs like you showed, so it might've just been that my heli vibrated a bit more than others. This is just another option. Keep in mind that if you mount yours on the right like I did, you'll have to reverse either the gyro or the channel. I can't remember which one needs reversing when the gyro gets flipped around.