What NMS said ...
An additional personal note -I've worked professionally (and personally) under the technically-fake first name 'Mac' for at least a decade, and it hasn't caused any non-trivial problems. Sure it isn't my the name on my birth certificate but nobody particularly cares. It is simply the name that everyone (apart from my mother) uses.
On legal type documents, I've simply used Firstname ("Mac") Lastname, and it's been fine.
I don't know about the US, but it is reasonably common here for people with non-English names (So: 'Chui Tsui Luoik' might simply list his name on everything as 'Eric Lee'.)
Heck, even Baz Luhrmann's firstname isn't really 'Baz'.
Even if it isn't advisable, technically you can sign any name you use to a legal document (as long as it isn't for the purpose of deception) - for example, you won't get out of a debt by pointing out the money is owed by 'Ron Midden', and that legally your name is 'Ron Maiden'!
However if there is a chance it will confuse people or give them an excuse not to pay you money, you probably wouldn't want to do it. Part of your job is always to make OTHER people's jobs easier.
One time to be careful is when someone else books your flights and accomodation for a meeting - if they book the plane ticket in the name 'Ron' you may have a bit of red tape to untangle ... not something you want to attempt at an airport ten minutes before your plane leaves, when you don't have photo ID matching the name on the ticket!
The only thing I'd do differently to NMS is in the contact info, include (Realname, writing as 'Pseudonym'). That makes it just a bit clearer - it is then obvious that they aren't dealing with two different people.
Mac
(PS: The US Writer's Guild has their own rules about what they consider acceptable in a nom-de-guerre. I believe they have quite a few limitations)