I've been thinking that 2:1 ratio textures might give good bang for the buck in some situations compared to square textures. Sometimes in car skins square 2k skins are little too small and square 4k are too big. The jump from square 2k to 4k is pretty big step as well as it quadruples the size (and there are no other good options in the middle?).
2k x 4k could be a nice medium spot. It is just double the size per skin instead of 4x. Plus it looks like it works really well for the car shape. And that shape also has the option of going 8kx4k as an upgrade from 4kx4k instead of going from 4kx4k to 8kx8k.
I wonder what happens in ac if you try to use different ratio textures together. For example 4x2 ratio skin file but 2x2 txmap?
Makes no difference , for example , if you are using a 4096x2048 UV basically a 2/1 ratio yeah ,
the UV is set to 2/1 ratio in my software its a custom UV I created ,
so for example I could paint my livery in say 4096x2048 , but then save it as 2048x2048 makes no difference will still load and be fine , also with the maps I can make them square again because the UV is custom it will simply stretch to fit the textures to the UV space that is programmed ,
I mostly see it on F1 cars going back to codemasters F1 2010 I believe there tires was made in say 2048x2048 scale but they compressed the map so something like 1024x512 scale ,
you can save any textures at any scale you choose will match the UV space , but you need to take into consideration the output quality of the DSS if you using PNG the compression is much higher , but not really any use in AC as hardly anyone uses it the engine makes the .png back to dds and causes extra load doing so ,
But if you create 2/1 ratio and nice settings and textures I personally believe its the way forwards , but only make it this way once the car is final as its a nightmare to work with if you make changes you need to reset the XYZ UV Xform again quite annoying but the end results I believe are worth it ,
simply because all my skins I am making are all 4096x2048 scale
EDIT , Say for example Dan
@A3DR makes a 4096x4096 texture for the Vortex ,
even though the ratio is not 2/1 on the UV , he can still save the textures as say 4096x2048 and they will be perfectly fine and still play fine , just have to check how the compression is , but either way its still be better than a 2048x2048 skin .