I am doing this PayPal project and a client asked me to set a fixed shipping regardless of the number of items ordered or their quantity.
The problem is, there is no form variable for a product item where you can define this behaviour.
After bumping my head for a while I realized the only way was to setup fixed pricing in PayPal profile.
And since that paypal account is used by multiple websites, the other websites have to override the shipping in form code.