Set a maximum amount for withdrawal charges

Hi, thanks for the great plugin!

I have a question. I’m going to make payments to my vendors using PayPal which requires payout fees of 2%, but the maximum fee cap is $20.

https://www.paypal.com/us/webapps/mpp/merchant-fees#maxfeecap

I know that WCFM allows me to add PayPal withdrawal charges by percentage, but can I set a maximum amount for it ($20)?

Thank you!