Optima Pro, plastic or cast aluminum knuckles?

[LoCoCNC]

There is a Optima Pro NIB on Yahoo! Japan. Looking at this pic it looks to include the plastic OT16V and not the cast aluminum version.
Is this what people have found to be the case with these? I am building one and like the idea of the plastic vs aluminum. Opinions?

[XLR8]

Hmmm, that's interesting!
I have at least one vintage Optima variant (an ebay find) with plastic "knuckles" and I'd assumed these were aftermarket pieces.
I seem to recall the bearings and screws fit the plastic part better than the die-cast aluminum version so I consider them an upgrade.