I beat Halo SLASO an i thought you might like to know how to get around the beginning... the rest i did in one try so it isn't to difficult, but u can check my video for tips.
It took me 45 mins total with all the errors i made in the beginning but i still have a time bonus of 1.5.
my final run starts at about 13mins in and i stop moving for about 5 mins to do my homework. (it was a good spot to stop and let Johnson and the sentinels ware down the enemy) I then did the glitch for the infinite laser ammo. After killing guilty spark i killed the sentinels with random weapons i found. I would suggest instead going below the walkway and using one of the ghosts.(i did not know about them yet). The rest is easy just drive carefully.