To make your prints conform to their own aspect ratio, and be sized according to your requirements, click on Custom.
Then select Special Sizes, Specify One Dimension.
You can take it from there.

After you get what you want in the queue, then just tell Qimage Print To File and Do Not Change Sizes.

Fred

First of all, Orientation lock comes off by default as you click on Custom Specify Dimension OK.
What size page did you tell Qimage you are using.?
What is the resolution of the image that became square?
What size print?
I want to simulate here.

If you forced a LOCK on a page size that can only work one way, ?
Need information here.

Fred

After some experiments, I can get it to almost work

What I want is a set of output images sized at 240dpi (occasionally 360), and (and typically 30" on the long side - all the same in each processing run). The smaller sides will vary (and I don't know beforehand what they are).

I have to set a paper size that the image will fit on before I start otherwise it creates multiple pages (even though I've set it to print to a file), however, if I set the page size to unnecessarily wide, it will add white borders to fill the unneeded space. If I have batch of images of differing aspect ratios there's no way I can see to automtically set the 'width' to fit. In practice, I will almost always have images of differing apsect ratios.

Unless there's a way to specify that the file should hold just the image, and shrink the image (paper size) to fit, I'm always going to end up with white borders on two sides of most images. 

Of course I can 'fix' this by opening the output files and cropping manually to the image border and saving again. I'd rather avoid having to do this if possible. (Or perhaps there's an easy way to 'trim' a file of excess surrounding white space (or red or whatever) space?)

I hope that explains what I'm trying to do.

Thanks Mike!
yes, that's exactly what I needed, hidden in plain sight!