How to Locate Seat Springs
 

We made our own rumble seat platform for an early 1930 Cabriolet but don't have the dimensions to locate the two holes used to hold the seat springs in location. The pins on the bottom of the springs are 26" apart and we're assuming that the springs should be centered on the width of the platform. We're not sure how to locate the springs front to rear, should the front of the springs be flush with the front edge of the platform? Or does does someone have the dimension from the front edge of the platform to the center of the hole that locates the seat springs? Thanks