Since you are not buried in responses I will take a stab at this, but, my only experience in micing is with harp & guitar so take this for what you will. As I remember the sitar it has commonalities with the harp in that it has a large body & long strings. For the harp I found one of the main problems was getting a good balance between the upper & lower registers, it was very easy for the lower registers to dominate the recording. The other problem is that if you close mic on the strings, the strings that you are closest to now have an over emphasis. My solution was to mic high, (roughly the top of the harp) with the mic pointed toward the top of the sound board, parallel to the strings, and close to the top of the harp. With the sitar being played horizontally (correct?) I would use a set of isolation style headphones while playing with the mic placement. I found the mic placement to be quite constrained on the harp (guitar seemed very easy comparatively), which did not allow for normal mic placement to get the best sound (I quickly gave up the thought of using any stereo mic techniques)
You could also look at what other people have posted for recording other string instruments to see what might apply
best of luck
