I have tested a way to extend the trial for this customer. There are prorate changes before adding trial we need to disable it and the customer would not be able to get a refund of the existing charged amount. Subscription after the trial end of 80 days would resume as is now with existing $395 charges.
No extra amount would be charged and no amount will be credited to the customer. We will be safe on both ends. Please let me know I can add 80 days trial when you will say yes. 
