How much fluid does the nano hold compared to a backpack? Unless it's massive, surely your having to refill it constantly with an increased flow rate? Backpack holds 22 litres I believe and on full flow you can empty this in minutes, personally I don't find high flow that beneficial when spraying chemicals as it causes overspray and run off.
It comes with a 25l clear tub but I use a 20 or 25l hypo tub. When I spray a roof, I add a bit more surfactant so I don't get run off. Many cleaners on the other forum have the Nano and now I know why. This job is all about efficiency and that trolly can save you a massive amount of time. You need a good spray nozzle which makes all the difference, I got mine from Rutland Pumps. After 3 jobs it pays for itself, I wish I bought it years ago. 😉