Category-specific Q&A

I am building a site featuring an “ask the expert” section.  I have 5 people (experts).  I have built a page for each, including a “ask john” and “john questions” type pages.  I created CATEGORIES for each (ask john, ask mike, etc.) 1) is this a good idea/best way with your awesome plugin?  2) I used the shortcut [dwqa-submit-question-form category=”catslug”] and set catslug accordingly (“ask_john”).  This works in opening page to ask question BUT the category drop-down is still there and forces the user to choose Category – 1) they may not see it and 2) it is redundant.  What am I doing wrong? and do you have any better suggestions?