So the Aircraft mod, this one. https://mods.factorio.com/mod/Aircraft-space-age I changed the setting in your mod, and it didn't change the size of the grid.

I might be wrong, but I believe the aircraft mod already has its own grid size settings, and this one should not overwrite that mod's

If it does I couldn't find them.

It appears something is blocking changes. I made changes to car and tank grind and nothing. They are the same.

Hm, after testing with a minimal modlist, the grid sizes are properly modified by the mod settings for this mod. It is likely that there is some kind of mod conflict.

As for the original issue, I do remember now, if a mod-added vehicle already has a grid, it will not be affected by the customizer mod, since it is assumed that those mods have their own grid size settings (at the very least, it is not possible for me to know if they have grid settings or not, so it is safer to not modify them in favor of their own balance)

For the Aircraft mod in specific, the only aircraft that will have its grid size affected by the values from this mod, is the Cargo Plane, because it did not have a grid to begin with. The Gunship and the other military aircraft will have their original grid sizes preserved. See previous discussion thread for additional context

If I had to guess, it is prob because of Bob's, which adds grids. To all vehicles

Oh yeah, I forgot all about Bob's Vehicle Equipment mod, and yup, that interaction makes sense.

Hmm, this does change the circumstances from that previous discussion thread. Just looking at the grid sizes for some random modded vehicles, they do appear to be applying some semblance of balance, acting in much the same way as my base vehicle grid mod.

While there is a mod setting to disable the grids added by bob's vehicle equipment (which would allow this mod to perform its expected functions), I think it would make more sense to override the grids instead. I'll add it as a setting (off by default) when I can.