I have a mainspring in front of me and the long leaf measures 2.337 long, thickness at tip .058 width .217. Short leaf length 1.686 long, thickness at tip .061. At fold .280. Opened .998

From Brophy's book "Plans and Specifications" it gives dimensions for an FW mainspring, over all length of long tip 2.236, short end 1.695, .055 at both tips. The drawing shows the mainspring compressed.
Dimensions for a Regular frame mainspring: long leaf or tip 2.233, short tip 1.797, .920 fully opened, top thickness .053 both.
Material: Chrome Vanadium steel, Rockwell hardness before machining B 98. After hardening C-46-50
Final drawing Jan. 4-36

Hope this helps, if you can file yours fairly easy then I don't think it is the hardness you want.