Hi silver,
Based on some 25 years of experience with four different ML models, 60" or so from the panel to the back wall seems to work quite well. And it's not only me. Others have tried this with much success. Seems to be the best place to optomize imaging, soundstage depth, and tonality.
Panel rake. Very near or vertical is my recommendation. Again, this is based on experience and has been confirmed by others. Can use the "string / plumb bob" method or buy a digital level.
Toe in. I'd start with the flashlight method so that reflection occurs with the "inner third" of the panel. Recommended by ML and others who have tried different positions. Key is to get solid center imaging while maximizing stage width. Vocals seem to be the easiest way to set but you can try some pink noise or other methods to confirm.
Back wall treatment. I don't favor absorption. Others like what it does. For me, it significantly compromises the "life and energy" of the musical presentation.
Powered bass driver adjustment. Very critical to get best sound. Too much bass or insufficient bass does impact
everything.
Suffice to say I've done numerous hours of listening and the above guidelines have worked for me. Your Montis are very sensitive to all changes in position and it may take some time to find the "right" spot for you. Please make sure you measure distances and rake angle very carefully. It really does make an audible difference and the best thing is it's free expect for your time of course.
I would urge you to experiment. You might be pleasantly surprised.
Of course as with all things audio, YMMV.
Good luck and most importantly, have fun.
Best,
Gordon
PS: Vibration attenuation is also extremely important to fully realize performance.