I'm happy to add a tunnel to Dimma if you would like to try that?
Config hints:
decnet routing 22.10
decnet node-type routing-iv
!
interface Tunnel4000
description tunnel to Stockholm 59.60
no ip address
decnet cost 10
tunnel source your-ip
tunnel destination 130.238.19.60
!
interface FastEthernet0/0
decnet cost 10
-P