Hi , i would also recommend the A-10C. There are hundreds of hours worth of fun to have with it.
As for trackir, i can recommend two things :
1 : Reduce your sensitivity settings near the center so you dont move around alot when near center.
or
2 : Do what i just did about a week ago , and DISABLE the horizontal and vertical axis entirely. You will lose out on 2 degrees of freedom naturally but it keeps the hud perfectly in view all the time. (when looking forward anyway) I personally like this alot, as i've also had problems with the HUD being partially not visible. Pain in the ass , especially if youre flying long missions and dont want to pause trackir or recenter it all the time.
That may be a bit extreme and its really personal preference , but for me it helps alot. There isnt much use to move your head vertically anyway. (You can manually adjust your seat's height in the A-10c with a switch in the cockpit)