I am going to attach several sources for your references. Further investigation is always good for our profession. This topic apparently worth further investigation.
1. IRS audit technique guide for partner's inside and outside bases
2. Publication 941, you probably already know
3. IRS Practitioner's Hotline number.(###) ###-#### ***** first choice is tax law question. Because you have an active taxpayer case, they will be glad to talk with you. They will have someone pre-screen our question first. Then, decide on whom to give to us to talk with. Sometimes, we get someone who is really good. Sometimes, it may not be the person's specialty. There was once I had an employee plan specialist calling me back like after I place the question for one week. You don't have to tell them the taxpayer information when you are asking the tax law question.
4. IRS held tax forums are held in major cities each year. The registration is relatively cheap. If you attend and ask around, it is likely that you will get nationally known experts on the subject. Otherwise, someone will introduce you to others to help us to get the questions answered. That is the purpose of the forum to help the professionals.
5. Find IRS rulings, private rulings on the subject. The authors are attorneys. They are also called, "the national counsel on the subject (IRC Code)." If there are things they don't know, they will research and get back to you. Most of the times, they can find resources for us right a way. This is not something we use all the times. But when we have definitely hard and strong questions, they are the resources we go to. A lot of times, the counsel's name and telephone numbers are placed in the end of the ruling. The reason for their contact information to be right there is for the practitioners to contact them on the subject. These counsels are usually located in Washington, D.C., they are very helpful.
6. Of course, when we are really not sure and the case is relatively important to us, we can always send in request for the IRS to give us private ruling letters.
Hopefully, these resources can help us answer difficult and specific questions. It is nice to have the discussion with you. Keep up with the good work.