For each payment method, there is the possibility to add a payment surcharge which is excellent. I use this usually for the "cash on delivery" option where courier services usually add a surcharge.
However, when in a single order there are products from two or more vendors, the payment surcharge is only added once. This does not correspond to reality. There should be an option to add the payment surcharge per vendor so, for example, if there are products from two vendors in a single order then the surcharge should be calculated twice (as there will be two shipments and therefore, the surcharge will be charged two times).
CS-CART, would you please consider adding this option?