Increase icon size on segmented button? (web 2.0)

So I am using icons on websegmented buttons. I think that the corresponding bootstrap element is btn-group. In order to increase the image size, I tried adjusting the padding parameters (down to 0rem) , and I added background position (center) and background size (cover). I played with font size and line height. No cigar.

1- Am I at least trying to adjust the correct element?
2- If it is the correct element, does anyone have an idea how I could increase the size of the image? It currently covers about 33% of the button surface. 75% would be nice. The Xojo picture added to the segment should cover about 75% at 1X resolution.