Projects Modifying Model A rear spring

I need to change my Model A roadsters rear spring. When I built the car I used a Posies 28-31R-C

• 46-1/2" perch center
• 2.5" drop
• 15.50" underside spring height
• 2.25" overall width
• 39-3/4" Eye to Eye
• Narrowed rear spring

It's hard to see in the picture below ,but the leaf spring has settled about an 1 1/2" and is causing the car to bottom on my torque arm. The ride has been terribly harsh. So bought this spring :29-31R 48-1/2" perch center . I've reworked the ends of the leaves :

I plan to run just 5 leaves and I plan to trim down the top 3 leaves to use as a shim on the bottom of the spring pack as to allow the clamp to clamp . I'm trying to decide how much to shorten the leaves that I'm going to use for the shim ? Bill

 

Most I have seen are cut around 6-8"