I always find Fiji’s classes are good for 30 minutes of intense practice. some suggestions…
There are some good advanced beginner classes too, for example…
It’s a good point about lunchtime slots though. I wonder whether it would be better to have the durations set at 15, 30, 45, 60, 75 and 90 mins. a lot of people only have 30 min lunch breaks, so it can be difficult to go through loads of classes that are between the 20 - 40 min range.
I hope this helps!