No, unfortunately I don't have much hardware tools beyond a digital multimeter and anything custom I make on a breadboard.
Using a ROM might be too difficult. Regardless, the idea is to find the resolution values together, which is likely a table. If there are other values inbetween, those might be the mode parameters. Then you find the specified values for the resolutions (blanking, front porch, back porch, etc.) and see if you can find those in the table, or ratios that match ratios of the specified values. After some trial-and-error, you might find a pattern that makes sense. Then you try changing a value and see how that actually affected the resolution (preferably on a multisync CRT that shows you the H and V rates). Repeat 100x
I'm pretty sure the TwinTurbo PCI card on my PM 8500 doesn't require a driver to work unaccelerated, and that it can change resolutions, yet it also has an extension that overrides these and was able to be modified for custom resolutions. So doing the Radius logo from ROM doesn't rule out the extension allowing customization in the same way.
Using a ROM might be too difficult. Regardless, the idea is to find the resolution values together, which is likely a table. If there are other values inbetween, those might be the mode parameters. Then you find the specified values for the resolutions (blanking, front porch, back porch, etc.) and see if you can find those in the table, or ratios that match ratios of the specified values. After some trial-and-error, you might find a pattern that makes sense. Then you try changing a value and see how that actually affected the resolution (preferably on a multisync CRT that shows you the H and V rates). Repeat 100x
I'm pretty sure the TwinTurbo PCI card on my PM 8500 doesn't require a driver to work unaccelerated, and that it can change resolutions, yet it also has an extension that overrides these and was able to be modified for custom resolutions. So doing the Radius logo from ROM doesn't rule out the extension allowing customization in the same way.