Well, personally I haven't used it but there should be a 3GB switch that gives you 1 GB more.
But in your case an option might be to try to isolate the parts that require all that memory in a separate application and turn it into a .net WPF application.
Since 12.5.1 there is an option to deploy as a 64-bit application .net application; it should be in the new features guide of that version. There are limitations though but you could check it out.
Ben