I really don't think it's going to be as simple as that.
Tonight, I installed QNX 6.2.1 NC version on my hard disk using a CD I had burned from the image I downloaded last night.
While the file was downloading, I checked the availability of the next version 6.3.0 and followed a link to an OpenQNX forum thread where a suitable unlock key for this had been requested and duly provided. Also in this thread, someone had asked whether the 6.3.0 installation was a two-stage process like 6.2.1, and was assured that it was not. Apparently, when 6.2.1 is installed, it asks for the CD to be removed while the system reboots, and when the QNX desktop loads up, you should again insert the CD which contains a repository of packages providing enhancements which can be installed in a similar way to the AmigaOS XL package.
Having seen this, I knew that if I could get QNX 6.2.1 installed, I would still be able to see the CD and thus have a good chance of a simple AmigaOS XL installation.
So, this evening I installed QNX 6.2.1 and then AmigaOS XL without a hitch, using a very similar method to the one I have already described for QNX 6.1, but all that happens when the emulator is launched is that an Amiga OS 3.1 DOS session is launched in a half-height window which will respond only to the AmigaDOS command 'endcli'. When this is entered, the shell closes and a Workbench title bar appears with zoom and depth gadgets. The mouse pointer responds to mouse movement, but nothing else is possible. The emulator is effectively frozen, and the machine must be reset.
At this point, it seems that AmigaOS XL is only compatible with QNX v6.1, for whatever reason.
PS. I had intended to download the QNX 6.3.0 eval ISO image
(523.63MB) tonight, but I've changed my mind after what happened earlier.