Vertical Spacing Between Two Treble Clefs

I want to create a system using a "Treble Clef" and a "Treble Clef 15 ma bassa" with the vertical alignment of 3 spaces between them. (That way, the middle C that is 1 line below the upper Treble Clef aligns with the middle C that is 2 lines above the lower Treble Clef ma bassa.) But when I try to set Format > Style > Page > Max Grand Staff distance down to 3.0sp, it seems to hit a lower limit of about 3.5sp and then shrink no further. (This might be some limit to prevent the clefs from overlapping each other.) The picture below shows that the two lines below the upper Treble Clef do not align with the two lines above the lower Treble Clef ma bassa. Is there a way for me to do what I want?