I have the V89 also but in a SBR package alla MP5k-PDW
I use the standard locking piece with the "k" marking on it which is a 16 LP. I use this with or without my Evolution 9 Suppressor and it functions 100 percent either way.
If you go to Rim County Manufacturings website they sell the 100 degree locking piece for like 25 dollars. I purchased one of these for my CA94 HK94 clone and the bolt gap was perfect and the LP is good quality and 75 dollars cheaper than HK.
The reason I bring this up is because HK ships the MP5k-PDW from the factory with the 100 degree locking piece installed. I am in no way an expert on LP's but if you have a 110 or a 80 degree LP you might as well go in the middle with a 100 degree. That makes sense to me.
If you search pasts posts you will see that this is a long standing debate on HKPro. So I would go with the factory and the middle of the road bet and install a 100 degree LP.