Great transformation so far!
Just a thought considering your grip issue and simply my $.02 without taking anything away from your awesome transformation. I think I'd change things up a bit and make it a little unique from the usual, average MAK-90 to Polytech/Norinco de-ban metamorphosis. You're almost there for a great Type 56 military rifle clone. The bayonet mounting assembly that's part of your front sight block on your particular style rifle was unfortunately neutered back in the day to allow the rifles to be imported. However, your front sight base is still primed for the addition of a "clamp on" style underfolding bayonet that looks almost exactly the same which can be found easily - as in the photo below:
And you don't even have to worry about any barrel threading for a muzzle break/flash hider as many Chinese military Type 56 rifles didn't have threaded barrels.
Additionally, a reddish Chinese plastic grip added would give the rifle a unique, military look. I preparing to do one in the near future to represent similar ones I found in Iraq as in the photos below. Also, the military ones I found were made in Factory 386 ("386" in the oval) which I presume your Polytech is marked with:
Again, just $.02 and food for thought. You've got a wonderful looking MAK-90 transformation there and well done!