I am never a fan of using tools without knowing where each calculation comes from. The MAC is pretty straight forward, but when you get into the safety factors and stab stability, it's not worth it to me to risk my investment on someone else's assumptions.

People give me a hard time at work for this all the time. Then I find a flaw in their tool and show them. It is better to figure it out and learn for yourself the first time, so you know what you are doing and can make your own changes. Then you can figure out if the tool is good and use it the next time.