I remember a thread where guys were discussing epoxy, aluminum foil, steel wool, who knows what else, on blocking the crossover.

I wish I could remember who said it, but it was along the lines of

'if you're gonna pack a bunch of stuff down in the crossover port, make sure to put $100 bills in there too, then when it breaks loose and gets down in a cylinder at least you'll have the $$ on-hand to fix it'...