Often you see a nice skin but it is not for your mobile. There was the possibility to resize all graphic gif files by hand. A long and hard work, I know cos I have done it.
But all the time there is a function in S4M to do that for you.
I just tried it from V3x to V3 and from V3 to V3x. Works fine.
There is still some work needed like resizing the wallpaper and the fontcolours are also not transfered, but at least all the graphic gif files are superbly transformed, V3x to V3 better then V3 to V3x.
Here is what you have to do (example V3x skin to V3 skin):
Get the V3x skin you want to change into a V3 skin and unrar it.
Open S4M with the target skin module, here V3, and save as whatever you like - after unchecking Light-Skin option.
Now open that freshly saved skin with S4M, uncheck Light-Skin option and straight underneath is the Import option, open that and go to the last of the 4 options, Pictures from Skin (resize), click that and now navigate to the V3x skin ski file and press open, S4M does the rest and all that you have to do is save the skin.
It is not a complete skin transformation, but a very, very big help.
The font colours can be imported the same way by using the second menu option in the Import option.