Great product but fixing jig handles snap off after a while,vessel hose folds under temp, vessel behind boiler not good design. Trap on 40kw not attractive and needs boxing, and Like you say heavy, the prv very awkward to change if necessary. The good things it will never block main hex due to design 22mm pipe, simple to service and I personally like them, you can have external vessel and use your own isolating valves. The main issue is service and back up, seems very old school in expecting people to wait till there ready rather then working with engineers/home owners to resolve things. I'm sure this will change, it has to if they are to be a successful manufacturer