I have the 340 and I put my SS grates in the dishwasher after every cook. No issues. Been doing it for about 2 years. I sometimes run it through twice. Hope this helps.
I thought you had to cut a hole in the grill to install the smoke daddy - if that's not right - please let me know. I would love to try one, just don't want to do anything to void warranty. Thanks in advance for your help!