Error when result set to more than 2000 while querying Fast Search Server for Sharepoint

Question

I developed a tool which allows user to select some Managed Properties (e.g. FileName, Author, FileType, Publisher etc) and a textbox to enter a search term. The result what we get is a tabular data which has all results containing this searched term and the values of Managed properties selected by user.

Now, when the user sets the maximum search results above 2000, we get an error:

System.Web.HttpUnhandledException: Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> Microsoft.Office.Server.Search.Query.FASTSearchQueryException: The search request was unable to execute on FAST Search Server. ---> System.ServiceModel.FaultException`1[Microsoft.Office.Server.Search.Administration.SearchServiceApplicationFault]: The creator of this fault did not specify a Reason. (Fault Detail is equal to Microsoft.Office.Server.Search.Administration.SearchServiceApplicationFault)

I'm doing initiating the keywordQuery object property like:

keywordQuery.RowLimit = 2000;

Just want to know what can be the issue. Does FS4SP has such limit for data ?