In my experience most of the free trials end up getting their payment bounced as Google does not care if users use disposable/dummy credit cards when they sign up for trial.
For example out of 20 trials, only 2-3 end up getting charged after the trial period ends.
It depends on the service you are providing and how you are getting your customers I guess, Apps like Hootsuite who are mainly focusing on pro users and have marketing channels outside the store dont even provide a way to register/pay on Android now, all payment is through their website where they dont have to pay the Google tax and controll refunds/cancelation.
If the first time users are encountering your app is randomly in the Play store it would seem its highly unlikely they would fork over money with no trial, you should try to improve the value so that you keep more users after trial, you can also increase the grace period maybe more payments will go through.
Android does have a high number of payments that never go through mostly due to non US users who dont use CC to pay, but as long as this trial period isnt costing you too much then shouldnt be an issue, you can also reduce the trial period.