Small Capitals and SizeFeatures

[KuznetsovAleksey]

Description

SizeFeatures of SmallCapsFont are directly bound to SizeFeatures of UprightFont.

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Minimal example demonstrating the issue

I set different SizeFeatures for different fonts to tune width of letters of small and large sizes in cm-unicode fonts designed in a single size.

For example,

UprightFont= cmunrm,
 SizeFeatures={%
        {Size=-6,  FakeStretch= ..., LetterSpace= .... },
         .....
        {Size=17-, .... } 
    },
FontFace={m}{it}{ Font= cmunti, 
  SizeFeatures={%
        ....

Fonts of all shapes and series are correctly tuned in such a manner, excepting the medium SmallCapsFont font.

Neither
    FontFace={m}{sc}{ Font= cmunrm, Letters=SmallCaps,
      SizeFeatures={....
nor 
    SmallCapsFont= cmunrm,
    SmallCapsFeatures={ Letters=SmallCaps,
      SizeFeatures={....
work correctly. 
SizeFeatures of the UprightFont are used in any case.

At the same, all sizes are correctly set for bold fonts and ssc-shape
  FontFace={m}{ssc}{ ... 
  FontFace={b}{n}{ ... 
  FontFace={b}{sc}{ ... 
  FontFace={b}{ssc}{ ... 

Is it possible to "split" SizeFeatures of Upright and SmallCaps fonts?

Further details

The settings are made via XXX.fonspec files.