I had already tried the method you suggested in the example above, its the method used on ESP32s of course.
And you get a compile error;
Compilation error: no matching function for call to ‘SPIClass::begin(int, int, int, int)’
Hence my original question.
And as mentioned in the OP, I could see the possibility of making the change in the library pin definition files, but was asking if it was possible to do such a pin assignment directly in a sketch …