I am running SAS/C in an emulated A-3000 so I feel close to your effort
The reason why I asked to try with the latest WinUAE.exe 2.5 is that quite a few issues have been fixed in the past weeks. We are going to push the update in a few days, after the dust settles a little bit and we are sure there are no last-minute issues. So for now you have to copy the .exe by hand.
If you right-click the system entry and select Edit, then go to the Configuration tab, does it show Top: 88 and Height: 512 under Screen Clip? These are the default values for the vertical offset, and I show them working fine.
Mike