Hi,
I just did what you suggested and it works 
It is a wonderful easy to use e-commerce plugin. I searched long for this one.
There is just one thing … you cannot put a maximum amount of the products. I often have only one product available, but the buyers can for example put the value on three products, and pay immediately.
How can you prevent this to happen? For now I put next to the product the number I have available 
Christophe
PS: I use it for a WPMU and earn some money with it. I’ll make a donation