I record a weekly studio presentation in a small studio (living room sized, ceiling is not extremely high) and right now I am using a wireless lav. I have two Sennheisers, one MKE 2 and one ME 102, and they both sound good - the sound in the studio is not perfect, but it's okay because there are lots of curtains and green screen carpet covering almost every wall and some of the corners.

Now I got this MKH-416 lying around and it is almost never used for anything, and that just breaks my heart ;)
I was thinking I might set it up in the studio to record the presentation - I already tried hanging it from the ceiling, and it sounded okay, but there was too much reverberation (I guess the mkh got most of this reverb from the hard ceiling directly above)

Would you say it's impossible to get a good sound with the mkh-416 in this room, or should I try pointing it at an angle and/or put some dampening stuff on the ceiling? I'm asking because I don't want to spend a whole day rigging that mic and in the end it was all for nothing...

P.S.: I forgot to say, it's only a one-person presentation in front of a green screen, and she doesn't walk around or anything.

"Shotgun" or interference-tube microphones generally don't work as well indoors, and especially in places with low ceilings or close reflective surfaces in general. The reason is because the microphone design relies on the timing and direction of off-axis sound to achieve its directional characteristics. But if the off-axis sounds have been reflected, then they confuse the microphone and it can not work properly. You have reported an excellent laboratory experiment that proves this.

I would continue using the lav if that is working for you. Especially if you have a less than optimal acoustic environment, you can minimize the ambient by increasing the direct to ambient ratio by placing the microphone closer to the talent's mouth.

Keep your MKH-416 ready to use when you wander outside for location shooting.

I think you would be better off with a boomed hypercaroid or a wired lav mic.

The 416 is no good for that. Throw it away. Just send it to me and I will take care of that. Haha. FWIW, this video was done with a single ntg-1 in a 14x13 studio with carpet on floor and muslin on half the walls. 8 foot ceiling. I used a rig that brought the mic down as low as possible just outside of frame and angled toward subjects.

I got tired of wiring on lavs and noticing in post that a wire creeped up from a shirt collar but I have to say they are much better.
A Parent's Perspective on Military Service - LCPL Spencer Morton on Vimeo

Not too bad but there is a very noticable "ring" of room reverb that changes the timbre of the voices. Whether this is acceptable or not depends on you - if the intent if for feature or broadcast I would have to say it needs improvement.

If you're moving around a lot, I'd go for a headworn mic. It may not make you sound "big and boomy", but it lets you have freedom of movement and decent sound. A nice big ole Neumann TLM-103 would be my choice if you can handle having a mic on a studio arm and keep your face close. That's the Howard Stern mic there.

Just to give you a good idea of the difference in sound between a headworn, shotgun, a lav, a dynamic, listen to these samples in our studio.

Sanken, RODE, Audio Technica, Sennheiser and Da Cappo microphones on Vimeo

For headworn mics, since it sounds like you're a Sennheiser fan, you might like the HSP2 omni. It has a very crisp, well detailed sound like the MKE2.

I also now like the new Da Cappo DA12. It has replaced my Countryman E6i, which I loved too...which replaced my Audio Technica AT892....ah the quest for the perfect mic is such a long pursuit......