How to get Fuse to use 4:3 on RPi4?

[BobbyJoe]

Hi,

Some of the Spectrum games from my youth won't run on lr-fuse, so I've ended up running Fuse where they all seem happy - but it insists on stretching everything to 16:9 on my RPi 4. I tried every retroarch setting I could find before realising from https://retropie.org.uk/docs/ZX-Spectrum/ that probably only lr-fuse will respect those, which explains why Fuse isn't playing ball. I've set the launch options to use one of the 4:3 settings and it's ignored. I've set everything I can find any mention of, anywhere, and nothing seems to affect it.

When running Fuse from inside PIXEL, it keeps to a nice 4:3 aspect ratio; it'll go fullscreen and stays fairly small but centred and 4:3. Running from outside PIXEL, from command line, it displays very small and refuses to go fullscreen (bad), but is 4:3 (good).
When running from retroarch it insists on stretching out to match the monitor resolution, and I can't find anything relevant on the forum or on the outside web about this. (On the plus side, full height, but...)

I'm on an RPi 4, and what I take to be RetroPie 4.6 as I've updated a week ago, having originally installed in mid-April.

Things I'd tried:

• the libretro basic options, Additional, setting video options for zxspectrum in there (but maybe only lr-fuse respects those)
• /zxspectrum/retroarch.cfg (again, if Fuse ignores them that was never going to help)
• the launch menu options when retroarch is launching the emulator with that rom
• removed --fulscreen as an argument to fuse-48k in /zxspectrum/emulators.cfg, just in case.
• /zxspectrum/.fuserc I've tried changing options around aspecthint and anything else that looked likely to me.

Given that there's a difference between what I get launching Fuse from just the executable, and what happens when retroarch is launching it, I'm hopeful that there is a solution, and that it's something that will be clear enough to people with retroarch knowledge and not just Fuse folks. But as neither option gives me something that's right, maybe there won't be a solution...

Any additional suggestions welcomed - I've spent so many hours searching and experimenting that I'm quite happy to try some more targeted experiments that anyone can suggest. Or if anyone just knows the answer off the top of their heads, that's even better :-)

Thanks!