This is anathema for some AK purists, but I found the standard length stock on my AK to be WAY too short and replaced it with an adjustable stock. Here it is showing the length difference between what it was and my preferred length of pull. This made a huge improvement in the shootability of the rifle and I have gotten my 5-shot group size down to 1.6" at 100 yards using the iron sights and cheap steel-cased ammo.
I don't know any AK purists! They are junk yard dogs. Whatever works!
Well I will modify that a bit. I would not normally mess with the stock that came with the gun. Read that if it has any value.
The MAK90 Thumb-holes actually have some collector value and not into other AKs enough to know.
So, if it has value as is, then buy an aftermarket to mess wiht, but again, if it needs to be changed to make it work right, then thats what an AK is all about, working.