[2005] 64 bpp image + GDI Plus + PNG = ???

I'm working with a bitmap that has .PixelFormat set to Format64bppArgb. As I recall, GDI+ likes Format32bppArgb or Canonical.

If I blit a 32bpp bitmap to the 64bpp bitmap, whilst resizing using the Graphics.DrawImage method, will I get more accurate interpolation? I plan on setting the graphics.InterpolationMode property to HighQualityBicubic.

Next, if I use the image.Save method of the 64bpp bitmap as a PNG, will it be saved as a 64bpp PNG (since the PNG file format supports this)?

If this doesn't work, do you have any suggestions? I need to save a 100x100 pixel image with it's alpha channel at 64bpp to a stream (which is read to a byte array and serialized with several other similar images). This is to maintain color accuracy for data analysis. I don't mind that my monitor can't display a 64bpp image without down-sampling to 32bpp. I don't need to look at the image. Just analyze it.