Small Ultra Modern UI and Page Backgrounds

What is the proper way of doing a "small" Ultra Modern installer with a custom page background?

In a full-sized installer, I'd use:

!define UMUI_PAGEBGIMAGE

!define UMUI_UNPAGEBGIMAGE

!define UMUI_PAGEBGIMAGE_BMP "${NSISDIR}\myskin\PageBG.bmp"

But, the addition of one simple line:

!define UMUI_ULTRAMODERN_SMALL

causes my page background to utterly disappear.

I've found that using:

!define UMUI_UNIQUEBGIMAGE

!define UMUI_UNUNIQUEBGIMAGE

appears to do the trick. But is this the "correct" way of doing things?