How to set alignment-baseline & dominant-baseline?

[felicksLindgren]

Creating my text element here, that i want to vertically center in a rect, but can't figure out how to set alignment-baseline or dominant-baseline.
I know there's BaselinsShift implemented but that just doesn't seem right to change when i dont want to shift the baseline I want to change it.

var text = new SvgText()
{
Text = "help",
TextAnchor = SvgTextAnchor.Middle,
Fill = new SvgColourServer(Color.Pink),
X = new SvgUnitCollection() { new SvgUnit(50) },
Y = new SvgUnitCollection() { new SvgUnit(50) },
FontSize = 20,
FontFamily = "Arial"
};

[cantax]

There seems to be no specific property for this, but Custom Attributes might work:
text.CustomAttributes.Add("dominant-baseline","middle")