The problem is every time you mention 1610 screws it makes it sound like everybody has to rush out and buy them?????? just remember to when you first started mister and how difficult it was. I use 1605 screws and belts on mine and it is more than enough for it's job, i could have my X axis twice as fast as yours with the belt but it would be pointless.

Thats it my rant is over and i'm stepping back from the computer for a cup of tea.