Networking messages data amount

Before I start, I want to make clear that my knowledge regarding this subject is quite basic. So I might say some things that will not make any sense.

Hello everyone, I'm working on a multiplayer game. I will not use the Photon Cloud servers, for the messages per second per room has a limit I must exceed.

Therefore I will hire my own dedicated server on which I will run Unity's MasterServer. I'm planning to use the function OnSerializeNetworkView to sync 3 parameters (Vector3, Quaternion and Float). I want to see how many users (max. 40) I can get in 1 scene simultaneously without lag.

-If my approach seems silly and you have a better one, feel free to tell me-

What I want to know is: How many bytes of data is in 1 message including the 3 parameters (UDP protocol if i'm not mistaken) that is sent to the server?

now, this question could be awfully wrong, so some explaination would be great.

thanks