Thanks for all the replies lads.
I'm still struggling to find a pellet the HW100 actually likes. So far H&N ftt are the best of a pretty disappointing selection allthough I'm going to start testing with slightly smaller pellets in the future as I've been led to believe the wheirauch barrels actually have an internal diameter of 5.51.
I'd been a bit dismissive of the high mounts but I think I should have an experiment. I suppose chairguns allways an option for comparisons at the very least.