Installing WB19 Site On WAS21 Installation (no replies)

Hi All

I understand that the WAS can host earlier version sites. I have installed WAS21 on a clean server and opted to allow it to host earlier versions. When I try and install a WB19 site it wants to install the WAS again. I have explicitly created the install where the WAS has to be installed on the server. So I have not created it stand alone with the WAS expecting to be installed. What could I be doing wrong here?

Cheers
André