either defective bushing, or.. whatever you may think. your trucks are tight. i've only seem muffin'd and blow out bones mediums on peoples set ups who's trucks are tight.
no bottom bushing, if your nut is below the top of your axle. they are tight. skated ace's for while. then indys, and now thunders. same bushings. even a blue bones upfront for the fun.
thats fine if tight trucks are you jam. got some friends who dig it. but your gonna bust through all bushings pretty fast that way. bones or not.