Hello Hiroyuki,
I downloaded your polygon reducer, and it worked great. Got a 20% reduction in polys with no discernable loss in quality. For me, I can use this well, even with the MDL5 limitation, just by doing the poly reduction and then converting to MDL7. I guess it would work better to do the poly reduction before animating. I would also encourage you to make another version that handles both model formats, but this is very usable as it is. Happy new year!!
Best regards,