Magento Issue: Paypal Charging Shipping Twice

I've just moved my online store to a new system using Magento instead of Oscommerce.  There are a few issues that arise and I was lucky enough to find  solutions for them. Nevertheless I'm writing this as my own reference and hopefully for those who are searching for the solution for the same problem.

Issue no 1: Paypal charging Shipping Twice.
I didn't realize it at first, however after having to refund  a few customers, I found out that Paypal was calculating shipping again after my Magento store already inserted the charge in the customer order. Therefore customer were charge twice for shipping instead just once.

Solution: After a few question to uncle Google. The solution was actually simple. There was nothing wrong with my Magento store. (I used the standard module which came in a bundle with the Magento installation). You need to change the shipping setup in Paypal. I had mine set to a value, therefore Paypal will add it up.

Login to Paypal. Go to My Account> My Selling Tools > Shipping Calculation. Change all your calculation to it to 0, therefore Paypal wil not calculate an extra amount for shipping when customer use Paypal to pay for their purchase from you Magento store.