I've never seen a performance drop in the data separation model ( #1 ) as long as the files are all hosted in the same place. So I wouldn't worry in your case, where the advantages of #1 outweigh the other option.
Unless there is another compelling reason to make your data be in SQL instead of FM, you are maintaining two systems and have other caveats of trying to make FM a "front-end" for SQL. Too many variables in my experience. I'm not saying don't do it, but be very clear on WHY it's necessary and learn all the 'gotchas' of such a method.