People keep trotting this out (and there is another conversation about the same topic) but there have been no experiments or evidence to show IPv4 + an addition

People keep trotting this out (and there is another conversation about the same topic) but there have been no experiments or evidence to show IPv4 + an additional options header for the additional address parts to have worked better, in terms of compatibility and/or vendor uptake. A similar issue came up when the internet migrated from class-based to classless IPv4 routing, and in that case, there were experiments that showed most networking gear continued to work and there was little to no adverse effect due to this switch.