Running Caltracs with XHD springs?

I spoke with Calvert Caltracs about running with XHD springs(already have them on the car)they said I could.Has anybody used the XHD springs on their car with these?I also have my original 6 cyl springs(kinda flat)and am worried about my big tires bottoming out using these.Any insight is appreaciated,before I make the call