The information you were provided is right -- a Tsunami will probably not fit into the On30 Shay. SoundTraxx makes a special decoder, numbered DSD-B2TS to fit into the On30 model. You should be able to order one of these from Tony's Train Exchange, Litchfield Station, Loy's Toys, or other SoundTraxx dealer.
http://www.tonystrains.com
http://www.litchfieldstation.com
http://www.loystoys.com
I was planning to buy a tsunami chip for my On30 shay but someone told me at the weekend that it would not fit.
Has anyone here fitted one and if so how did you fit the chip in?
Thanks alot
Kathy