Hello again lurker888,
finally managed to get to the writeup - I don’t want to use more of your time, but feel free to have a look http://forum.mikrotik.com/t/quick-guide-bidirectional-1-1-nat-snat-dnat-setup-w-working-example/183024/1 - if you have any feedback for me, I am happy to edit!!
Many thanks again for helping us on this one!! Jürgen