I think part of the issue is the bolt up design, the bolt doesn't hold the material solid enough and will flex. If it was me I'd get a swingarm off Ebay, cut off the existing chain adjustment area, and machine the extensions to slide into the swingarm about 4-6" then you could bolt it or weld it and they'd be solid. I've built numerous sets this way with no problems, one set is on a ZX-10 bike, no issues what so ever. I was pressed for time and had a set built (KX 250), the first trip out they tore up a new sprocket and my extensions, home they went and were modified, no more problems, I still don't like them, so I bought a swingarm and am going to make another permanent set up