over50
‘Sounds’ like you have a solution (pardon the pun).
I have just one Tsunami sound decoder. I found it was a challenge to get it to run at very low speeds. Other people have experienced this with Tsunami diesel decoders too. There is a solution. It involves playing with a few CV’s but it works. If you don’t get the low speed performance that you want, you may want to study this thread:
http://cs.trains.com/mrr/f/744/t/216137.aspx
Dave