1986CR with 39mm PWK Air Striker

To all our 2 stroke jetting professors i have a question in regards to setting up a PWK air striker on a 86 cr250. I have an 45 slow jet a 175 main a NEDW needle ... clip in number 3 position. The bike is all stock with the exception on an UNI air filter. At 1500 ft elevation normal temps and pre-mix is 32 to 1. My question is what number slide will work best ? Currently it has a #6 . A # 7 is leaner and my some info i have read suggests a #7 . Duncan Racing says #6 is the route to go... If a #6 goes in a 125 why go leaner for a 250 ? Thanks for any input.