you are defeating the accuracy of the tool, by it's intrinsic simplicty, adding invariables of unknown valving and flow of said valve. all you need is the tool, and 2 slip on rubber plugs. synch 2, stop the engine, swap the hoses and plugs, synch the other 2, stop, swap and do the final.
the one reason i love the twin max is that it is a comparitor between 2 sources, when you add in the valve, and the possibilty of variations internal to the valve, all bets are off.
I have a bunch of those valves, I had almost 800 gallons of aquariums at one point. I would not rely on them to flow equally.