The foobar DSDIFF plugin in that article is no longer maintained and the author (kode54) removed it from the foobar website already. Here is another plugin:
https://sourceforge.net/projects/sacddecoder/files/foo_input_sacd/
I took a 32-bit float 352.8kHz RMAA reference file, converted to DSD64 and back to 32-bit float 352.8kHz again with different settings. Multistage and the bundled FIR filters, except the 30kHz one, created too much ultrasonic noise and RMAA is unable to analyze them, so I only analyzed what RMAA can analyze, with an additional 1023 points filter I made (attached). Should be able to avoid further frequency response/ultrasonic noise excuses.