I will post your message because it’s always helpful for others for solving hair modding problems and maybe someone else has an idea!?

 Sims3 is easier and the easiest are the Sims2 meshes but the Sims4 have the most details which is also interesting when it comes to accessories but the Sims4 ports need more time because of the uv mapping, reducing faces etc.

I have ported two Sims4 hairstyles, which were no problem. It also depends on the Sim creator. For example Nightcrawlers meshes have per se a high poly count..(Sims3 version).. The problem is to reduce the number of faces so that you will still get a detailed mesh. If you reduce too much the hairstyles look really bad as I said: too compact or lifeless.

You will not find much about this topic in my tutorials.

I tried it yesterday again..and I saw that when I extrac the Sims mesh as a Blender file with The Sims4 studio and then load this blend save, the number of faces has doubled! Sims4 studio said e.g 24.000  and in Blender they are doubled. I don’t know why. I’m testing now the decimate  tool in Blender 2.79. I hope it will help to preseve the mesh details. I’m using the Dragon Stone hairstyle for testing..maybe I can get it to work. Looks like you got me on my “modder honour” not to give up :D

You could use the LOD2 version of the hair which hasn’t so much faces but it is possible that you can’t make the face sorting ( when you use Blender 2.49) because you can’t select, the single strands of hair. You have to tried it if it works for the style you want to port.