I bought a Stihl MS441 magnum for milling 20" logs, I believe it is similar sized as the 365, I can tell you I wish I spent the extra $250 and picked up the MS461.  It works but it is work.  Unless you have other uses for the saw or plan on doing some milling over several years, I would just hire a portable mill to come cut up you lumber.  A lot less work and time.  Around me it is $275-300 per 1000 board feet for a potable mill.
BTW- get the ripping chain, day and night on cutting ease.