That is pretty cool, I love these types of DIY projects.

The accuracy of the flow bench probobly won't matter much, as long as it has decent precision. I'm guessing it will be used to measure *changes* in flow from porting, etc, so the actual number dosen't matter much, as long as you note how much the flow increased/decreased, from "stock" you can get a good idea of how well it works.

Keep us updated. Pretty neat project.