ALL my mechs are adjustable center pin.
I have about 3 chiyou
a king, astro, nemesis, stingray, m16 sentinel and private v2.
the private v2 was the only one that didn't seem adjustable at first, but actually it, is, it's just difficult; you have to use a long nosed pliers to reach down inside the tube to do it.
the m16 sentinel is actually spring loaded, so it's a newbie friendly centerpin.
the stingray is totally loose! you just screw your topper on; then when you screw up the rest of the stringray, you just screw everything thing in until everything is snug; the only downside/trick to that is it means you don't have a sealed centerpin, so you don't want to put something like a carto or protank on there where liquid can leak down.
On many clones the screw head isn't slotted or hexed or roughened in anyway but you we can just do that ourselves using hacksaws or files.