I'm a heavy person also, I have broken many spokes on the back wheel, both sides of the wheel so that's not uncommon I would say. I've only broke one spoke on the front wheel and that was back in the 80's ! Just more weight on back wheel pure and simple and the offset of the spokes isn't a plus that's for sure. I've had them break at both ends of the spoke. Learn to repair it yourself is best advice. Also buy a tension meter it's helped me build a very evenly proportioned wheel that needs very little to no truing or only a breakage every so often..