I mean I know I could, but has anyone done it? Is it stable?
Are there any cheaper alternatives?
Only if they're made by children in a third world country by a company owned and run by children in a third world country, I'd imagine. Those things are dirt cheap as it is.
Edit: ahh, forgot the Rockstand versions are the pricier ones. There are cheap generic ones that do the job just as well (I just bought one) for peanuts. Go with those. eBay has ALOT of them.