Customize the report margin while rendering

I want to customize the report margin while rendering. I am using ReportExecution2005.ReportExecutionService  webservice to render report. how to customize the report margin?

I try to use deviceinfo for this and set the below device info, it is not work out. It always render the report with design time margin. Is it right approach? Are there any issue on below deviceinfo?. Thanks in advance.

<DeviceInfo><PageWidth>11in</PageWidth><PageHeight>8.5in</PageHeight><MarginTop>.25</MarginTop><MarginBottom>.25</MarginBottom><MarginLeft>.25</MarginLeft><MarginRight>.25</MarginRight></DeviceInfo>

Best Regards

Senthil

Developer