What is the difference between {MONOFRAMEWORK} and {MONO} ? Arent they the same?
Also changing the framework with ms works like this:

Oxygene MyForm.pas /assemblyname:MyForm /type:winexe /frameworkfolder:C:\WINDOWS\Microsoft.NET\FrameWork \v2.0.50727 /ref:$(Framework)\System.Windows.Forms.dll /ref:$(Framework)\System.Drawing.dll /ref:$(FrameWork)\System.dll

So with /frameworkfolder you tell the compiler what framework you want to use. Next /ref:$(FrameWork)\System.dll uses that path.