To make it work you need to route it via your public GW and NAT, so it does not leave the router with your 44.x.x.x IP. I think this is a little bit wrong, not to be able to access the portal from a random HamNET IP.
Well, it *does* work from a net-44 IP but it requires sufficiently well setup of the routing... When you have routing setup from the old days (like "route all 44.0.0.0/8 to the radio network") it will not work.
It works OK here from my net-44 IP but still I could envision this would cause problems. E.g. just at the day the portal was down for the move, one amateur here wanted to move his system from the IPIP net to our local BGP routed network and he was unable to delete his gw. So he first setup the GRE tunnel and BGP routing but it did not work due to restrictions at our GW (having both IPIP and BGP does not work) and of course then he could still not reach the portal after it was back up. But he managed to do that from an external IP.
Maybe the portal should not be in one of those 44.190 networks that are not supposed to be on IPIP, but it should be in another net-44 subnet that is both BGP routed on internet and IPIP routed on the mesh. Then it would work OK.
Rob