RE: H9 Spitfire Build
Warwix, just a bit of advice on your choice of retract servo; the HS75BB will not handle the extra weight of your up grade to Robart struts. The Hitec retract servo will fail, burn out due to not having enough torque to raise the gear against the slip stream forces when flying.
Your best retract servo to use is the JRPS791. The Hitec is rated at 92-114 oz inch torque while the JR is rated at 260 oz inch torque. The JR may be twice the price of the Hitec but you will never have to replace it due to failure like the Hitec. You will be lucky to get 10 retractions with the Hitec, before it fails. I replaced the Hitec with the JR on my H9 Spitfire two years ago, it has 50+ retractions and I have never ever had a problem with it since installation,I also have the Robart Struts installed.
You have a very clean looking engine, muffler installation on your Spitfire, and the 3 bladed prop really tops it off, I like, I like it a lot. Good luck, and have a very safe and pleasant flying season with your Spitfire.
Roger