A short heads-up for people who have fitted the P+S Technik IMS Mount system to their RED ONE cameras and may want to shoot in 2K with cropped sensor and may like to have optical viewing through the taking lens.
P+S Technik have relisted their B4 Mount / optical viewfinder for the IMS mount system at a heavily discounted price here :-
It is uniquely designed for a 2/3" or Super16mm sized sensor camera, the SI2K. The unit entirely substitutes for the IMS B4-Mount. A B4-Mount lens fits up to the front of it.
As far as I am aware, there has only been a limited production run on the viewfinders which are apparently based on the Evolution finder for ARRI motion picture cameras. We here in Western Australia have taken two for SI2Ks as an optical 3D pair so there may not be many left in stock.