boot.cfg not being read on virtual machine

Hi,

On a Mac M1 Studio I created a virtual ARM machine using the NetBSD-10.0_RC4-evbarm-aarch64.iso. I used UTM, a Mac program that provides a GUI wrapper around QEMU. Trying to get the largest screen size possible (1024x768 !)I found I had to issue ‘gop 2’ at the boot prompt. Rather than do this manually, I wrote a simple boot.cfg and put in in /. Unfortunately, when I boot into the VM, the system doesn’t seem to see boot.cfg — i see the NetBSD banner and then the system boots after 5 seconds with the default ‘gop 0’. My boot.cfg looks like this:

menu=Boot using 10x24x768:gop 2;boot
menu=Boot single user:gop 2;boot -s
menu=Drop to boot prompt:prompt
default=1
timeout=5
clear=1

Am I missing something obvious here?

thanks,

Steve