Please add some settings for zombie chases

Dear creators,
Please add an option to change the frequency of zombie chases! I just finished 2 missions and had just one zombie chase, in 1 hour. I would really like to have boosts more often - like each 5-10-20 minutes.
Many runners will appreciate that. Thanks in advance!

illi4 about ZRX: Zombies Run + Marvel Move, v1.1