Prior to the Owin version of the self host webapi it was possible to define the MaxRecievedMessageSize like this to allow for larger files transfer:
var config = new HttpSelfHostConfiguration(baseAddress);
config.MaxReceivedMessageSize = 2147483648;
Is that possible with the Owin Selfhost approach?
You can write your own OWIN middleware for that. Kiran Challa wrote an example that suits your needs at the asp.net forums, http://forums.asp.net/post/5622974.aspx