If this assumption is correct I think the best thing to do would be to complete the rack in the Rack Layout environment, then perhaps save the whole rack as a new symbol (drag it into the Library List under My Libraries), then drag it into the Pictorial Schematic document and scale it there.  Or you could copy it from Rack Layout and paste into the Pictorial Schematic, then Group it prior to scaling.

Note that to scale the rack you will need to check Options | Scale Symbols, and then you should either use Arrange | Scale to set a scale factor, or drag a corner handle with the Shift key held down on your keyboard - this maintains the proportions of objects when you scale dynamically by dragging.

I hoep this is helpful - please let me know if I have misunderstood what you want to achieve.

To scale a rack symbol down to the correct size in pictorials use a scale of 10.36% - this converts 19" to 50mm which is the scaled width of a rackmount product in the Pictorial Schematic environment.