How to set the font size of ITextElement if only know Height of the text?

Question

When I read text elements from a .dgn file. I only can get the "height", "length" attribute of the text (it doesn't have a "size" attribute) (example: total height = 0.9; total length = 8.6).

I need to add these text elements into a PageLayout of Arcgis. I used the IFontDisp to identify font attributes for text. It requires to identify the "size" attribute. How can I know that ?

ITextElement pTextElement = new TextElementClass();
IFontDisp pFont = new StdFontClass() as IFontDisp;
pColor = new RgbColorClass();
pColor.Red = 0;
pFont.Name = fontName;
pFont.Size =  **???**
pFont.Weight = weight;