I am shooting a project and we want to test out the 4.5K. Everytime I have shot with RED its has been 4k HD and then transferred to Pro Res 422 or 444 quicktime files 1920x1080. HD will be our output kind of defeats the purpose of 4.5 but we want to test it nonetheless. When bringing it into final cut will we just make it the same 1920x1080 pro res files or is there a better way?
While Color supports 4.5K files, FCP will not be able to Log & Transfer the files in. You'll therefore need to use something like Clipfinder to convert the files to ProRes 422/444.
Whether you intend to online with the ProRes files or not should determine the debayer settings and resolution you convert to, but the important thing to remember in any case is to set your Scale Mode to 'Fit Width' for the conversions in order to maintain the correct framing. You will be left with 16:9 files with letterboxing.
You could then online with Color for best results and finish at up to 4K.