Agreed. I think about custom controls like I think about cryptography libraries: most hackers aren't specialized enough to have thought through all the corner cases and unless you want that to be your specialty, you're taking on a lot of risk of blowing your own leg off (metaphorically speaking) trying to hack out a solution instead of using something (ideally) well-maintained and with some history behind it.

(Having had some experience working on custom controls in a browser: it's the kind of project that will occupy a three-person team at a Fortune-500 full-time over multiple quarters to get right. Set your expectations accordingly.)