Nice tool! As mentioned before I nowadays always use the robart airline restrictors, 2 in series which is adequate. When you're gonna test these it might be interesting to make a view glass for some kind so you can actually see the flow rate. I made this set-up many years ago from a syringe, M5 threaded aluminium cap glued on. At idle you can see the drops falling down, approx 3 drops per second. All commercial engines have the restrictor inside the engine. I elect to keep it outside so I am able to see fluid on the other side..or not and stop the engine.
I used yours as well, worked oke. I turned the outside a bit smaller and squeezed it into the fuel line as shown;
Set-up on all my current engines;