I wouldn't slam the door on the SpitIX, though I understand your grief. Here are some tips though:
The SpitIX is good at altitudes between 10K and 20K, it has more legs at that alt vs typical run-type fighters. You can out-run N1K and other's at that alt, where on the deck they will run away easily, or catch you easily, depending on the situation
Second, if you want to fly the SpitIX, look for fights that are appropriate for it. Typically, these include fights were you know the enemy can't really afford to run very far. I.e. show up at a base capture where the enemy has to stay close by lest he give up the base to a capture. The Spit can really do well when the enemy knows he can't/shouldn't run. Don't do fighter sweeps at 25K, there are just too many runners up there with a 30+mph advantage on you.
Third, fly the Spit light, only take 50% fuel and a drop tank. Ditch the tank just before you the fight. This will make you light and believe me, you should run outta ammo long before you run out of fuel. It should help you acceleration a bit to give you a quick shot before a runner can run.
I typically have flown the SpitV more than the IX lately, but the concepts are the same. Luckily the SpitIX has more power to compete, where that extra lack of power really hurts the SpitV. My squad had a Spit sortie the other night, 5 of us went in, 5 came out, 15+ enemy didn't.
-Soda