I am kicking myself a bit for getting crazy last night with it, haha... what I did was push it hard enough to exit the coil completely from the gap by a large amount -- the 12" frame supports 50mm of one-way travel not counting frame thickness... 59mm with frame thickness... and 71mm with vent spacer thickness added -- minus 8mm for triple joint ring so we can go 63mm one-way before bottoming the ring... and we have 62.5mm in the motor... so I had it up around 60mm one-way (which is actually 5mm PAST surround linearity)... which makes the coil about 1/2" past the gap *laughs*
So when it came back down it knicked the top plate and knocked loose 1/2 of one voice coil (the coil is an 8-layer bifilar which is wound as a quad; so you can knock out 1/2 of a coil by breaking one wire) and this wire is rubbing on the top plate now making that metallic sound (I can see the loose wire through the vent spacer -- WOOPS!!!).
Either way I have some ideas to minimize that possibility; although, I must admit, I was being totally careless with it to do that!
Needless to say it was pretty crazy and just me being too happy with my new toy