Yup!

Excellent!

The sunroof drains are in the front corners of the sunroof. Open it up stand on the door sill and look under the lip, you will see them.

My car is outside in winter storage, so forgive me if I'm memory challenged here, but I think the drains are visible at the very rear of the right and left side of the sliding roof, when fully open. I think they exit just forward of the rear wheels (or just behind, I really can't remember), look like tubes. You can try compressed air into the drain holes and see if it blows out like it should.

Edit: Just read last post, and holes are in the front, not back.

I do recall discussing with a MB mechanic friend some time ago a water problem that he had spent some time on for a customer, similar to yours. He said that the sunroof drains sometimes leak into the inside of the rocker panel, and the accumulated water finds its way into the floor area. Checking this would entail pulling up carpeting though, but it might be the problem.

OK. Thanks. To verify a little something about the sunroof. If the drains were indeed stopped up, wouldn't there be water standing in there? I guess what I am saying is, shouldn't it be obvious whether or not it is stopped up? When I looked at it today, there was not even any dampness in there and we had a heavy rain about 3 hours before I had checked it.

Not so much a matter of them being plugged, but that the path for the water is straight through to the outlet, as opposed to a leak in the tube/pathway somewhere (rust, eg.) allowing it to exit inside the body (inner rocker panel, eg,). Perhaps someone who has had hands-on experience can clarify if the drainway is a steel tube, or a non-metal (plastic, vinyl) tube. If steel, I can see how a partial clog could allow water to sit long enough to rust through a small hole allowing water to get diverted into the rocker cavity.