I can help with FOC, but I can't give you a tried and true elk arrow setup.
In terms of foc, here's how I normally build an arrow. First, I try to find out what I want in terms of a total arrow weight. Lets just say low 500grs. I'll then find the shaft that I want to use. We'll use your choice of arrow for example, 8.4 gpi. For my length arrows, that would mean 235.2 grains for the shaft. Add 13gr for the nock and about 12 grs for the feathers. Now we're in the ball park of 260gr (+/- because the shaft length may change during tuning due to tip weight).
Now here's what I prefer. If I can add weight to my carbon arrows, I'll add the weight to the tip given that I can get the arrow to tune to my likings.
My choice would now be to play with a weighted insert or heavy broadhead. It looks like you can only use a cb insert with these arrows? If so we need to go with about 20gr for this insert. If my math is correct we're at about 280grs. So now I need to find a broadhead in the 220-250gr range to get to my desired total arrow weight of low 500s. So for me, I would go with the 250gr broadhead of my choice, since they make it in that weight.
Now if you can't find the screw-in broadhead of your choice at the specific weight, the cool part is that there are many glue-in traditional broadheads with many different screw-in adapters of varied weight and size. They make these adapters in aluminum, steel and even titanium. This should make for a broadhead in your weight preference.
Keep in mind that adding this much weight to your tip will change spine, so tuning is a must. For example if your current set up has a 125gr tip with a standard insert and your arrow is already coming near to your riser at full draw, you may need to bump up in spine which will in turn add to your total arrow weight because of the change in gpi.
Given this system, I'll usually end up with a foc between 17-22%. Most of my arrows fall in the 19% range which gives me a "more forgiving" arrow. Personally, I've been seeing benefits in tuning, penetration, wind drift, etc, giving me a "more forgiving" hunting arrow.
On a side note. Given my results, it doesn't "nose dive" out of my rig. In the past, I've bare shafted out to 60yds (just to experiment).