As stated above, {HEAD ~ the situation} of {TAIL ~ the center} of gravity can be adjusted by a partial cut of the block, formation of concaved part, etc 
As stated above , { HEAD ~ the situation } of { TAIL ~ the center } of gravity can be adjusted by a partial cut of the block , formation of concaved part , etc
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH