Hi FAUguy,
This is less likely to be an issue when the mattress is on top of your foundation and frame but the knickerbocker foundation is certainly a very strong bedframe that is longer and has a support leg closer to the end of the mattress which would reduce the chance ot tipping when you sit on the end. Post #10 here also has more information about choosing a steel bedframe and some of them would also be similar as well with a support leg closer to the end of the mattress.
Phoenix