Codename-74

Customizer always shows all the skins at once i.e. 1x/2x/4x BUT - it doesnt work without "proper skin mod" selected.
Say if you use a "2x skin" on a "1x mod selected" model - it will be just whitish complexion skin showing up and not the actual skin. once you select 2x skin on "2x mod selected" model, it will work. just make sure you have to use everything in activemod to be that way - i.e. eyebrows/lips/pantyhoses/tattoos/stockings etc.

You can put 1x/2x/4x in same folder - it will automatically work accordingly.
Say if you want to use 2x resized skin on a 4x model. Resize skin to 2x and put tha along with the 4x skins - once you select 2x mod and reload the room again, in customizer - skin will load the 2x textures. If you wanna go back to 4x - just select 4x mod again, reload the room and voila back to 4x. or you can simply put 2x folders separately - to identify those easily, your call!
 
Below are some screenshots that may be of some help:

1. Addon folder glimpse

 
2. Game scripts which actually brings 2x mod selectable in customizer. (this comes with game updates)
2. 
 
3. A glimpse of example 2x skin folder in activemod. note that i have also resized eyebrows and lips.
Best way is to look/browse in addon - images folder (example in screenshot 1) in order to understand what files are considered in 2x sizes.
 
4. selecting the 2x mod and "reloading" is necessary for it to take effect.
reloading means - quitting the room and reload it again. (Alt+R is not considered reloading.) this works similarly to body/facemod use in VX.

 
5. Selecting the 2x skin after you have reloaded the room/customizer.

I think i have mentioned this in my guide, and also now, that when copying save folder from v7.5 to vx, dont copy "portable.reg" file, because it contains registry of v7.5 and that when you copy to vx installation, it will only cause path conflicts.