Verdant Meadows Abandoned Aircraft Graveyard aka Old Airport:
Open firerange for helicopter, but also for rockets, and lot of cover.
Valle Occultado 'Tee-pee-Motel':
Limited cover, but only attackable from north (tho limited), east and west.
Valle Occultado:
tiny place, good firerange for heli, not attackable from east. Good cover.
El Quebrados:
much cover, but some interiours that should be prohibited (namely Ammu and Tatoo) plus refill (machine) on the street.
Clearly attackable from all sides.
Aldea Malvada 'The Lost City':
Very good firerange for heli, limited cover.
El Castillo Del Diablo:
few cover opportuntities, but these are good.
Wide field to spread upon.
El Castillo Del Diablo - Las Brujas 'Ghost Town':
Good cover, limited attackability. Event allready happened here.
Sherman Dam:
limited cover, very good to attack.
Fort Carson:
Good cover, good firerange, good area.
Octane Springs Oil Field:
Limited cover, but good firing range for rockets, good attckability tho dangerous fly-by.
Hunter Quarry:
Limited attackability, limited cover, balanced area.
Tierra Robada, Toreno's Mansion:
Very good cover, trees complicate attacking
Green Palms Raffinery:
Unbeatable cover.
SF Bay, small ship:
small, covered place, good to attack
Bayside Marina:
not much but usable cover.
SF Bay, big ship:
Good cover, small space. Loading bay should be prohibited.
SF, Paradiso Park:
Good cover, complicate attack thru trees.
SF, Diner @ Juniper Hollow
Limited cover, good firerange.
SF, Paradiso & Palisades & Juniper Hill Backyards
COVER FTW!
SF Santa Flora Medical Center:
God cover, Heli can be forced to fly low by hiding deep inside.
Las Barrancas:
Balanced Area, wide field with good hideouts.
SF Bay, Beach Party Island:
That might be something special. No cover, perfect attackability, good luck!
SF, Esplanade East, Pier 69:
small place, unlimited cover.
SF PD:
Good cover, very complicated attackability.
Doherty Destruction Site:
Good cover, limited but good attackability.
Big Smoke's Crackfactory:
Much cover, good to attack.
Shady Creeks:
good cover, very limited for heli due to near Mt. Chiliad and Shady Creeks Forest.
Whetstone Highway Xoomer:
Not much cover, but the few remaining is certain, not really attackable from the north due to forest.
Santa Maria Beach Pier:
good cover, unlimtied attackability.
Mullholland:
Very limited cover, but splitting over different building stages might bring the win.
LS, Little Mexico, LS Atrium:
Hardly any cover, complicated to attack.
Verdant Bluffs:
Win for the heli. orly?
Jefferson Motel:
Home of 'Reuniting the families', the 'Jefferson Motel Madness' and now of 'Hunter VS Rocketlauncher'.
Las Colinas (in the background, left) would also be a good location.
Palomino Creek Backyards:
This time without cops
Awzum cover, easy to attack. Interesting fights.
Los Santos Forum:
Home of the famous 8-Track Race.
Open field, no cover, unbeatable firerange.
LS Ocean Docks
Lots of cover here, great field, good hideouts, very attackable. Awzum.
K thats it for now, if i find anything else i'll let ya know.
Edit: FFS now im tired x)