[commiefornian]

Doubling the header size by switching from ipv4 to ipv6 would be significant for systems that nearly always run at 1200 baud half-duplex or slower and have significant packet loss.

If any of your pings actually routed over the RF link from some gateway, it is quite likely that you saturated the link and effectively DOSed anyone on the frequency of that link for miles. So while it looks like they aren't on the internet, it is because you knocked them off of it (and any HAMS attempting to use that frequency for any purpose would also have been DOSed).

It makes much more sense for everyone else to move to ipv6. The normal internet is many orders of magnitude faster and more reliable so leave ipv4 for the slower/higher loss protocols.