If asking this to a kilt-wearing Scotsman, his answer might be "nae, maam, it's as good as it e'er was." But because this is the Japan forum, I'm asking about Yukata etiquette at a ryokan.

So what is appropriate underneath when wearing the Yukata in public areas of the ryokan (esp upscale ones)? Are sweats too informal? How bout a t-shirt and gym shorts?

Also, if the ryokan serves dinner in a dining room rather than in your room, what is appropriate dinner attire then? I'm headed to Hoshinoya later this summer, then Gora Kadan a while after that, and I'd like to limit the extent to which I cause uncontrolled laughter.