Thanks to all for the valuable info./comments! Agree that Rotax is an example of liquid- cooling success. Still, prefer slower turning, direct drive engines. Our project will remain air-cooled, and as simple as possible. I may be influenced by long term affection for old Triumph motorcycles (and now the Royal Enfield 650 Interceptor). Would a remote oil tank, i.e. increased oil capacity, be worth considering ? Is monitoring two rear cylinders cht adequate, or do we need monitoring of all 4, and egt as well?