a target (fita, ifaa, naa, nfaa) archer doesn't care a fig about penetration. it's an ultimate consistency game. the form rules are more rigid than hunting in order to promote better uber consistency. hunter's don't have the luxury of standing upright, with vertical bow, careful foot stance and timed draw/anchor/hold/aim/release.
since formal target game venue marks are at distances waaaaaay further than practical hunting distances, arrow tracking is important for both stability and wind penetration considerations (not target penetration). hence, the 9% nibbs instead of 7% that were popular in the 60's & 70's. some fita archers go much higher, and their bows are in the hunting holding weight class.
imo, designing and building an arrow for formal target archery is lots different than that for a hunting arrow.
while some fita archers are holding good hunting weights of 50#, most are in the high 30's to mid 40's. reaching 50 to 90 meters with low trajectory is the name of the game, then add in consistent accuracy in outdoor weather conditions. with a 40# holding weight, you want the arrow speed needed to reach out and touch that gold with as low a trajectory as possible. 8-10gpp, for an arrow weight of 320-400 grains - not exactly built for hunting penetration even if the foc is above 15%.
as in the topic starter's case, there are archers who treat 3d as a formal archery event and will use 35-40# bows ... some even go the freestyle route with a stickbow. i see no benefit of efoc for that kinda archery. imo, once you get up to around 15% foc, that arrow is gonna track just fine and, in my own testing, i found no flight benefit of rebalancing the shaft for more foc.
if you treat a 3d event as hunting practice, then none of this thread matters at all. use yer hunting holding weight bow and heavy arrows with whatever foc floats yer boat and have at it. as you should. because you're a trad bowhunter and not a target archer.