Sure, first make sure every joint is tight—any leak throws off the pressure reading. Measure the static pressure with a manometer at the fan inlet and outlet, then plot that against the flow rate you get with a low‑flow meter. For a weird shape, lay out the loop on a piece of cardboard, run a thin tube through it and watch where the air slows; that’s where you’ll need a larger pipe or a less restrictive bend. Keep the path as straight as possible, use 90‑degree elbows only when you can’t avoid a sharp angle, and always leave a small gap for air to fill in. Test with a real fan at full speed, record the numbers, tweak the pipe diameter or the fan speed, and repeat until the curve fits the design. Patience and precise measurements are the only ways to get a true, repeatable loop.