I wish I could help here more but I am not the guy... I don't know of a setting in dnn but here is a post that says the following :
the following way you can disable or enable stack trace in web.config
past here as a quote didnt work for the info below...
<> trace enabled="false" localOnly="true"
with <> around each of those lines above in the web config is what this thread you can do for an ASP.NET app... so DNN should be included in that arena should work.
there is the link I found that info, could this work?