It's really a late comment for this topic but I' ll try to give some tips and suggestions about Flip Flop trophy. First of try to do it on solo or max. 2 players because the more player means more quicker you die. I tried with 3 more people and died at 24(2) and with 1 more player and died at 25(2). So I say don' t waste your time on Co-op or with randoms. If you unlocked Tier 3 maps, then Solar map is your best friend because it has 2 camping spots and 1 of them is near at the Weapon Armory (the safest one) and go with the Heavy Class because has Goliath and EM1 laser gun. Just be careful for Nano Swarm attacks and Warbirds, Drones etc... You can reach 12 waves really easy without using Goliath. After wave 13, just to be safe wear the Goliath and start killing enemies but leave one of them alive so you can run, escape from him while recharging the suit. Then kill him and turn to the spot. Be careful about objectives, if there's an objective about Defuse and Uplink just don't do them. You' ll get a punishment but again leave one of the enemies alive so your punishment will end without havig a trouble and be careful about turrets. Upgrade your weapon to lvl 5 or 6 then fully upgrade your armor. Then buy the last 3 upgrades for the weapon. Try to buy Exo Cloack or Exo Stim ability, they're really important for this run. When you receive Support Drop don't select Dingo because it makes you slow. Try to pick up Unlimited Sprint first. On streaks pick up Goliath, Bombing Run or Assault Drone. This Drone is really helpful for the Warbirds but not forget to destroy it because it can cause you a problem when your Goliath didn't recharged. Then rinse and repeat this Goliath method and be careful. Unfortunately the game not pauses and it will take your time like 2 hrs 45 mins. to 3 hrs. Really long process but it will worth it. If you got further questions ask me. Good luck!