Setting up a specific PDF quick viewer

[Free4all]

How do you specify the PDF Viewer to be used for the internal viewer and quick viewer?

I first removed .pdf as Windows Preview extension in Tools → Settings → Programs → View → Viewers.

I then tried specifying the executable for PDF-XChange portable in Tools → Settings → Programs → (Internal) Viewers, but it has no effect on the quick viewer.

As a side note, for the internal viewer (as opposed to the quick viewer), the selected file is not shown even though the %ActivItem% parameter is specified, but it does work for the internal viewer if %ActivSel% is used. Neither works for the quick viewer, however.