Don just shooting from the hip here, some one else may see this a little better then I am. If you have a reflexed profile and when you string it it goes directly to a D tiller, sounds like the outer portion of the limbs are weaker. I am not meaning it is not shootable just tillered so that the outer portion is taking all the stress. How do I know this? LOL I have a tendency to over work the outer portion of a reflexed bow, very easy to do and it will bleed LBs like you hit its Carotid artery.
Now to answer the simple part of your question, in theory shortening the non working area by 4 inches still leaves you with the same working area of limb. Non working area is in this case not an issue unless you shorten the working area of the bow by more than you shorten the non working area. Dang thats like talking from a merry go round, lol. Hope that makes sense.
You might (bite my tongue) post a full draw, unstrung and a braced pic and let some on here see if I am right about my hunch on the tiller. It helped my understanding of how to work the limbs of a relexed bow and helped me make a better shooter.