Some good suggestions (and some not so good!). However, you should be considering more than just cloud base. In marginal conditions, you need to give yourself even more options than you would perhaps normally plan for. So, at the expense of longer route and more time in the air (which is why most of us fly anyway for enjoyment), minimise hostile terrain and route by more airfields you could divert to if weather deteriorates. Also, practice D&D pan.