Are you trying to upload the package via the GUI? If so, 2gb is your limit. You can have the SH pull the package from a server, but I find the easiest thing is to just push it via SCP. There was also a bug with wget (which is used to pull) but that should have been fixed it all recent versions.
You can get pscp.exe (from the maker of putty) at http://the.earth.li/~sgtatham/putty/latest/x86/pscp.exe
pscp.exe my.pkg admin@steelhead:/rsp/packages/
You'll be prompted for the admin password and it should upload from there.