You will have to make an new .esp file to do it. In the Construction Set, go to Gameplay on the top menu bar, and down to Settings, and scroll down through the list to fActorStrengthEncumbranceMult and change it to whatever value you want.
Actually, I had created a mod like you suggested, but it would not load into the game, so I assumed I was missing something fundamental. Turns out it is a win7 problem. The mod works fine on my older XP box. I remember seeing some posts with similar problems, so I will check them out for solutions. Thanks again...