I said it was possible. Sub 4:09 is, also, very much possible. You can shave ~2 seconds just by getting on D-Horse earlier after fultoning the truck driver. You can make him spawn right next to you if you point your camera at the right direction at the right angle.

Tasks, in order of completion:

1. Secured the rough diamonds hidden in Spugmay Keep.
2. Pinpointed Kazuhira Miller's whereabouts.
3. Extracted the transport truck driver.
4. Extracted the commander from Wakh Sind Barracks.
5. Extracted Kazuhira Miller.
6. Completed the mission without being discovered by the Skulls.

00:08.368 - Run starts/ Load 1 starts (cutscene fade in) 00:17.301 - Load 1 resume (last dark frame) 01:46.217 - Load 2 starts (cutscene first frame) 01:49.434 - Load 2 resume (last dark frame) 02:21.634 - Load 3 starts (fast-travel iDroid screen disappears) 02:27.400 - Load 3 resume (last dark frame) 03:30.334 - Load 4 starts (fast-travel iDroid screen disappears) 03:36.034 - Load 4 resume (last dark frame) 03:50.668 - Load 5 starts (cutscene first frame) 03:53.851 - Load 5 resume (last dark frame) 04:45.184 - Run ends (chopper door closes)

If there's something wrong with my timing I'll fix it as soon as possible.