I've had to try to reposition the lever spring on a number of levers. Some like many Shimano are easily scavenged from other levers, Campy's Ergos use the shift blade's hub spring for the brake lever. Many levers don't have such broad use/availability or easy access/replacing of the spring. So if you strike out and if you can use that lever on the front brake. The shorter cable run will result is less casing friction losses. Additionally some calipers have an adjustable spring and if so then increase that best you can. Andy