I contacted Michigan Wheel and filled out their form for prop selection:
http://www.michiganwheel.com/MIWheel...is/InboOne.asp and then emailed one of their tech people who were very helpful in figuring out how I had used the form incorrectly. I'm very pleased with the 3-blade prop that they recommended for my A4 with a reduction gear.
If I had a direct drive A4, I would contact Indigo
www.atomic4.com/ to inquire about their 3-blade prop.
Prop walk is an issue with my Bristol 35.