Each of the FT planes recommends throws for low rates and high rates. Start with your Tx at 100%, on the servo, use the inner most hole, on the control surface, use the outer most hole. Then move the sticks and see how much the control surface moves. If you want more throw, move the linkage outward on the servo, and/or move the linkage inward on the control surface. When you get the linkage adjusted to move the surface a bit more than you want, use the Tx to reduce the throw and dial it in. If you need to go below 75% on the Tx, select a different hole for the linkage. As you reduce the percentage, you are loosening resolution.
If you can, get an experienced pilot to madden your plane. All planes are tough to fly until you get the trim dialed in. When they are trimmed, they are much easier to fly.
The spitfire is not a beginner plane, it’s built for speed, not stability, it’s more of a 2nd or 3rd plane. I recommend learning to fly on a trainer type of plane. When you can fly the trainer, inverted, across the field, you will be ready for the spitfire.
Here is a link to some beginner planes
https://www.flitetest.com/articles/top-5-beginner-ft-planes
