Yes I have the lance from Northern tool and I use the scoop on an old universal pole I have.
They can and will kick on switch on and switch off, so before you start it or stop it, raise it at least 1' above the guttering before activating the trigger at least until you get used to it.
It could cause damage to the guttering if you switched it off to close and all this can happen with the narrow jet fitted that's when it becomes a bucking mule, the chances of it causing damage to a roof are much slimmer because I recon your gutter tool would snap first.
Training is the answer to any power tool and the lance is no exception
