Bought a new to me 2388 last week and have never ran an airfoil sieve. It looks like both the upper and lower are airfoil design. From everything I've read it sounds like it wants a ton of air and open the lower as much as possible for air flow. I tried opening it up quite a ways, but started getting a lot of trash in the bin. I have read that a lot of people blocked off the front part of the sieve with a "ripple tin" kit. I will try this first but I was just wondering what the basic settings are to get started. Can't seem to find a lot of advice from any companies that sell this type of system. Any advice would help. Thanks.