I can understand why you choose those 3 perks but I don’t think its the best way to use Elder Stalker, that spec is only really good when you can stack with down range for that 150 damage. And disk is probably a better option than spear at this point, specially for Elder.
Players that I know that started using Elder as their main use lens, down range then for third perk modified reserves(for more plasma shots) or adrenal boost(so that stamina gets full faster) or large pouch (even though if the mission is short the Predator won’t even have time to use all 4 medkits). Worked well for them.
For the medic/large pouch combo, I think Jungle/Hunter its the best + down range, even though I used lens for a long while I was conviced to change it.