The main issue I see is with the variability of metering itself... There are two common ISO standards in use, and there are four possible that could be used (three by CIPA standards). And they give different results. Even calling them "standards" is a bit of a stretch.

Especially the the REI standard (Recommended Exposure Index); which is used for most DSLR's, and is the only standard applicable to recording raw files. REI commonly rates ISO (and exposure) at least 1/2 stop low compared to a more directly measurable standard like SOS (Standard Output Sensitivity).

This is the Canon R5 as measured by DXO. Note that while DXO disagrees with the manufacturer's ISO ratings, it's because they are using a different standard to measure by (I'm not sure if it is Sat (saturation) or SOS).

Part of the reason the recommended exposure (REI) is set low is to protect against the harsh highlight clipping characteristic of digital sensors. And that's why there is usually "recoverable" highlights in a raw file.

So I would say your best bet is to spot meter the highlights and then determine how many stops over results in actual overexposure/clipping by taking test images and editing in post. Note that highlight warnings on the camera's image review also tend to "lie" because they will typically report as clipped anytime any one of the color channels reads 255 (or close). And they are showing the processed jpeg (not raw file); so you really do want to verify by editing the files in post.