change gunner upgrade to prox scan
change ir smoke to APS
IR is good as gunner on the likes of dawnbreaker, zavod
can keep ap if you want, I prefer sabot
I use auto loader although I don't think it works with sabot that well so might change to reactive armour
burst fire when in gunner seat, no more than 1-2 bullets
use HMG, again no more than 1-2 bullet bursts
for repping, you shouldn't let the tank get less than 75% imo, although it depends entirely on the situation, if you only have 1 or 2 engis with rpgs, I wouldn't really worry unless HP goes below 50 but if you have 3/4+ guys then jump out straight away as soon as the tank takes damage and start repping although if the situation is really bad then the tank driver should be backing up
When repping, always try to go behind the tank as not only will you be covered but if needs be I can back up and push you back to so I don't leave you behind, of course if the enemies are behind the tank then don't go to the back of the tank
APS blocks any rocket/rpg except TV missiles, you know it is working when you see a green light, once you see a red light, it is down
might as well shoot at aircraft but only if they are close to you, no point engaging them when they are half way across the map