Retired Maggie MG it's and they soundcdelaminated

It is best not to try a DYI rebuild on older Tympani’s.

One other problem is the wood frame warping on Magnepans made before 1987.

In 1987 the IIIa was the first Magnepan that did not have frames that warped, and they solved the delimitation problem, mostly, (if you keep them out of sunlight).

Magnepan still rebuilds the old Tympani speakers (replacing everything but the frames) and they will not delaminate.

Let the factory do it right, and not try to save money.

MGII's won't reproduce super low bass.  Are you over-driving the panel? Sounds like you might be getting "panel slap".  That will happen if you overdrive the panel or just put too much low frequency information through it.

I've redone a few Maggies. Since the socks are off, can you locate exactly where the rattle is? 

My method was to reglue, let dry, then hook up with the socks off. Play some music for an hour or so, just to make sure nothing sounded "off". Next, which is the most important, is frequency sweeps. I'd run 15hz to 20khz over and over...listen very closely for any type of breakup or rattle...put your ear right up to the panel...as close as you feel comfortable doing at a loud level. I almost always found at least one rattle on each one I've done. If you have a computer that you can hook up to your DAC or any output, you can download a program called Room EQ Wizard that will do custom sweeps and all that for you. 

Running a frequency sweep is very important. Really helps you find those little spots you may have missed.