Jean-Marc,
An easy way to check your system and to know if you are going thru Internet or thru ampr.org is to ping my IPIP gateway at either 44.151.91.7 or 44.168.12.6 If the ping time is around 300ms you are coming in from Internet via ucsd.edu and if the ping time is less than 100ms you are coming in thru the IPIP tunnel.
For testing purpose, you can just manually create a few IPIP tunnels and routes on your openwrt router. . Feel free to contact me directly as I am only a few km (Bures sur Yvette) from your QRA. You should even be able to connect the 44.168.x.x network via radio on the 5.7MHz band.
73 Remi F6CNB