Miro,
As of 18:38 GMT the IP of tunl0 is 44.60.44.2/24. I previously used this address, there was no difference in behavior. I've also used 44.60.44.0/8, same results. According to RFC 2003, tunl0's IP is arbitrary as it's IP is not used in encapsulation. The only difference is that the Public can now access my tunnel interface.
Using 172.31.255.254, packets left my border router as IP-in-IP with source 76.114.216.250 and destination of 109.107.73.62 when pinging 44.185.1.1.
The encapsulated packet left my 44gateway as source 44.60.44.10 destination 44.185.1.1.
-Lynwood KB3VWG