Are these bushes okay for use on unsealed roads? I think pretty much all of my rear suspension needs to be redone (especially the big bushing in the diff), and would prefer to replace them with polyurethane ones for better handling (may also get bilstein dampers and new springs). The road is only about 3 km long, and I drive slowly on it anyway. Harshness is already pretty bad, so I figure it cannot get worse. Thanx!

In a case like this, I'd doubt you'd notice the increased harshness from poly bushings. Its more noticable if you drive relatively smooth roads - when switching to poly bushings gives you more info on the road texture through your gluteus maximus.