advisor/tech ratio

What is an acceptable number of advisors in a shop with 10 techs? My Service Department is a GM/import store (Olds Buick GMC and Hyundai) with 8 journeymen, 2 mid level apprentices, with a dispatcher. Number of RO's per day is usually about 40,(seperate Ro's for warrantee and CP).During the slow winter season we usually do about 800-900 RO's per month. More in summer. We have a Warrantee administrator to code the warrantee RO's. We have 2 writers and a service receptionist. The 2 writers are (I feel) overworked and don't have enough time to do any upsell or research on vehicle history or recommended services. Any thoughts?