[mst]

Yeah, and because it's a heavy device, one need a collar...

Yes... I remember using that lens once, and that copy had a Kirk or RRS collar. Very solid construction that supported the lens both in the front and back. But also quite huge, of course. And ugly, too

I do have an AF-S 300 in the lab, btw... just not the AF-S 300/4

-- Markus