I've been working on the main gear doors, these arnt big and are in the fuz. Mick suggests using servos, but I've gone for small air cylinders. The rear bulk head is conveniently positioned to attach the top of the cylinder to and a since the door moves through 90 deg its quite easy to estimate where abouts it needs to connect to the door (ie approx the same distance from the hinge as the cylinder travels - 20mm in this case. (plus a couple of mm to allow for the fact that the swing of the cylinder is reducing its effective length a bit)

...I done lots of thinking and then just decided to guess - and it seems like a good guess since when the cylinder is closed so is the door and when fully open the door is at 90 deg! Hurrey!