GIMP :: Loading PNG Images Into TImage32 At Design-time With Delphi 2006

I have a series of PNG images which have been authored from various sources, but mostly with Gimp. The images have transparent backgrounds and use partial transparency effects like drop shadow, etc. I want to display these on a bitmap layer of the TImage32 component from Graphics32.

I have dropped a TImage32 component onto my form, with the intention being to set the visibility to off, and use the TImage32 as a container for the PNG image I want to draw on the layer.

When I go to load the image at design-time, the dialog has two tabs - it allows me to load the RGB image, and the alpha channel, and I don't know how to produce these - I prouce the image by using the export to PNG function of Gimp. If I load the exported PNG into both the RGB channel and the alpha channel the resulting image doesn't have the transparent background. There obviously must be a procedure I need to follow to get Gimp to produce both the RGB and alpha channels.