More Ultimate-er Miata Door Bushings

This is a remix of Apple Dongle's well received Bushings. I noticed that the original model wasn't large enough to adequately stiffen the door jam. This "more Ulimate-er" version is about 1mm wider for a snug fit with the door, giving a satisfying ka-chunk when the door closes. The diameter of the slots, on the original version, was so large that the M6 bolts barely overlapped the plastic on the bushings. The slot has been resized to fit these bolts and ensure that the bushings are stronger near the bolt heads.