What is the recommended height of a dropdown menu that has an internal scrollbar on desktop?
I have a dropdown menu that when opened could contain 30 - 50 items to choose from. It's for desktop. I want to accommodate users with 1024 by 768px screen but I also don't think it will look good with a dropdown list that runs the length of the page and then scrolls. I was thinking of setting a max height for the dropdown and then using internal (nested) scroll bars to view the list. See below for example
I know the pros to showing full length means easier visibility of more options to select from but if 80% of time users are selecting the first 16 options is it the best option to display as much content as possible. If I was to go fixed length on the height is there a recommended height it should be (e.g. in pixels or by number of selections? Or are there guidlines to follow ofr recommended height (in pixels) for desktop dropdowns that have an internal scroller?
Below is an example of fixed with with dummy content.