Thanks for the advice, I will have to keep that in mind in the future. I've tried exiting my scenario, changed to a P3D Maule, set texture res to 4096, then saved. Selected a new airport, loaded the scenario with the Maule, and it still defaults to 2048. I tried changing back to 4096 within the scenario, but it still reverts. Might be an addon that's overwriting, I just can't seem to find out which application is doing it. If I don't solve this by tonight, I will most likely try a fresh install, and install each add-on one by one, until I find the culprit.
I have a C172 Trainer from Flight Illusions and SimKits coming in, so preparing for 4k before they arrive.