I have used a custom sql snippet to add some charts to a custom report. It works okay, but there are two problems.
1. When the name of the snippet is too long, it moves the close button and others out of sight. I had to use inspect on the browser and shorten the title to make changes. Anyways, i deleted it and used a snippet with a shorter name afterwards
2. There is no documented way to parameterise the sql so that we can continue to use the date range dropdown. It would be nice if this were possible, otherwise, it reduces the utility value of having custom reports.