If I were you I would do skullcrushers, just like you said...more stretch. Here's a quote from Vicious from the Customizing HSt thread (which I highly recommend you take a look at) on exercise selection to help you decide for yourself though.
1) Highest priority. You choose compound movements for coverage. Although different compound exercises may be better at hitting areas than others, really that isn't your primary goal. Neither is overlap (the volume thing), which should be low-to-moderate. You want to make sure you're covering the muscles you want with exercises that you like and can properly HST with.
2) You choose isolation movements that increase stretch with load. If you don't do this (i.e. you choose tricep pushdown over skullcrushers), then you're not making enough differentiation between doing an isolation movement or simply doing more sets of the adjunct compound movement. For whatever bodyparts that you don't do add a stretch-point isolation movement, THEN you consider increasing overlap and add more compound movements from different angles or grips.
3) Lowest priority and usually optional. You choose isolation movements to increase load at contraction in order to emphasize burn. This is nice for adding hypoxic stress with a highly efficient means without wasting time or glycogen and over-fatiguing yourself. Unfortunately, most people, when adding isolation movements, do 3) instead of 2) For a bodypart, you shouldn't consider 3) until you've done 2) If you don't add isolation movement for burn for that bodypart, THEN you look into adding more sets/exercise for that part.
Thus, your exercise selection should create a trickle down effect on issues with volume, specifically # of sets/exercise and # of total exercises. Whatever the case, you should follow this order of priority with the exercise selection.
Case in point:
Shoulders. I do military press and db laterals for the delts. I'm wondering if the laterals are really unneccessary.
This is an example of doing issue 1 (military press) but doing issue 3 (db laterals) without having done issue 2. You would either throw out DB laterals altogether or add flat/incline-bench DB laterals to emphasize stretch.
