Since the information provided to increase performance with this mod is rather difficult and hard to understand (at least for me) I'll provide a step by step basis on how to increase your FPS and remove the stutter issues after extended play time.

BEFORE ANYTHING Go into your audio settings ingame, disable VOIP if you are doing singleplayer and with Superb Survivors/Subpar Survivors; this will give you more frames and processing. And is easier to do than the following.

1. Go to file explorer, find your steam directory with your common games. (steam/steamapps/common/ProjectZomboid)

2. Locate 'ProjectZomboid64' which should be a JSON file; open this with notepad of any sort.

3. Now you'll have a few lines of code to view, there are two specific lines that state "-xms1800m" and "-xmx2048m". Don't let the style of these lines scare you, the xms stands for minimal memory load and xmx is maximum memory load, leave the xms line alone; Adjust the xmx line to what GB of RAM you have in megabytes. Since I have 32gb of RAM but want to allocate 16gb (Cause 32gb for a game like this is excessive) Id change it to "-xmx8132m" for 8GB or "-xmx15748m" for 16GB. If you only have 8GB of RAM then the default settings are the highest you could technically go without altering PC settings.

4. Save, and play the game!