Handling Of Png Background Transparency In V3.72+ Options

[mrwarper]

Hi everyone, long time user of ancient versions (pre-name changes), new user of current ones, first post.

After doing a bit of research I'm afraid I'm not clear on how [newest] PMView handles transparency so I thought I would ask here...

I have a b/w png with its white 'background' set to transparent. It is used on a web page, the idea being that the image won't need to be touched to match the background color if it ever changes. Looks as it's supposed to in SeaMonkey.

Open it in PMView 3.72, 'save as' (Type: PNG, 'transparent': checked; -- Options: 'use transparent color if possible': checked, 'allow use of palette for grayscale': checked). Reload in the browser and poof! image has a solid white background -- transparency is gone! Tried other options with the same results (binary-identical output files).

File -> Info as reported by PMView:
Before save) No. of colors: 2, Color Type: Grayscale, Bit Depth: 1, Transparent Grayscale: 255
After) No. of colors: 2, Color Type: Grayscale with Alpha, Bit Depth: 16

What am I supposed to do to preserve transparency in old images?
Any recipes to save PNGs with transparent backgrounds in the newest PMViews?
Are b/w images handled differently than 4 or 8-bit images with transparency?

TIA.