The problem is the HW97 and 95 are designed to be running at over 12ft/lb, so running them lower creates a slow shot cycle. Even at 12ft/lb its not perfect and a lot of people short stroke them. I think the twang was due to how loose the spring was on the guide as the guides are probably designed to be used with their 12ft/lb springs.
I'd get a 12ft/lb spring for it when you order if I was you, it'll be cheaper than buying one over here. I would have done the same but for some reason the place I bought the HW95 from didn't sell a 16j spring. I ended up going for a Welsh Willy tuning kit as I'd heard great things about them, but wasn't impressed for the money it cost. I can recommend Vmach if you ever decide to go down the tuning route, but just fitting the 16j spring and giving it a re-lube with some decent moly grease should be enough to get it shooting nice.
The HW97 is a little fiddly to take apart, but there are lots of guides on forums and Youtube. It should be a lot easier with the weaker spring in as there shouldn't be much preload on it.
I think my next purchase will be the HW77 with the summer forest laminate stock. I fancy a decent rifle with open sights.