Just an update. The IO didn't ask about the source of my monthly transfers. They only cared that they were all a FTT. I did bring tax documents (proving my self employed status) and documentation that the money was transferred from a business account and not a personal account, but again I wasn't asked for anything. It was just a shot in the dark the IO would look at them. I don't want folks to think I'm saying documents like those will help in any way.
I do recommend having all you documents in order. She appreciated (told my wife, not me) I highlighted the areas of my bank statement to coordinate with the credit advices. She also appreciated that I transferred money on the same day every month. Not saying these things increase your chances, but I think the IOs like when they can just breeze through a complete and organized extension application.
Also, I have previously done the 400k method three times, so maybe that was taken into account.
Like everyone else has said, it's a 50/50 chance you'll be asked. If you're reading this and fall into the same boat as myself, my biggest piece of advice is to come organized and hope you get the right IO.
Thank you all for the good info.