Disclaimer: this may or may not work, but if you don’t mind getting into the menus and making adjustments, it’s worth a shot to at least rule it out.
On my TV, lx3 mode requires the TV aspect to be 16:9 and lx4 requires the TV aspect to be set to 4:3. This is for Genesis, Saturn, SNES, N64 so I guess it should be the same with other consoles including the Wii.
If changing the multi mode doesn’t work, try changing h.samplerate. From stuff I’ve read, not all displays are affected by adjustments to h.samplerate, but on mine it changes the width of the displayed image.