How to set par2 files sizes to never goes up more than 50 mb or 100 mb .

Hello . Please help if I have 1 gb rar file or even 10 gb but I need par files that multipar creates to never go over 50 or 100 mb each no worries about time to create or storage or cpu usage. How to get it done. NOTE.. I use the py script to create the par2 files. Not sure what to edit. Thank you