Sorry I wasn't able to get on tonight- I'll keep an eye out for you... it is pretty tough to get with 2 player-- I think it alot easier by doing it with 3 player where I quit after killing the land spawn guys.
If we try this, Unless you are decent at flying the heli, you should try to find the one of the rocket launchers-- there is one near the east stairs on the 5th floor.... (2 floors down from the roof)-- there is another one on the 3rd or 4th floors near the middle of the building. If you die, you get to keep it.... so you should be the one to try and take out the boat-- while you can do it with the rifle, the rocket is easier.... just aim a little ahead of it...
Let me know what you want to do in the mission.... fly or take out the boat and I'll let the other guy know (if we play with him)
If he isn't around, we can try it with 2 player....
I do suggest you go ahead and do some public games just to get the feel of the mission.... find the rocket launcher and perhaps try to take out the boat.
//edit//
Congrats on the trophy...
I got on right after I wrote that and RPG was online... we did several runs but just couldn't manage it on the fast building clears... I destroyed a few helis for us
(I'd been drinking a bit tonight)
Finally I saw someone come online from GTAforums (superjude) that I'd done BDB II with-- he actually was one of the people that shared the "noose" quitting strategy/glitch for the superfast times -- I invited him into the game and we just kind of applied it (quitting) to deal breaker-- I quit and let them finish them up... 6:55 (it wasn't exactly a clean run but got it done in one run)-- mics definitely help with working out strategies... I highly recommend the quitting strategy for 3 player dealbreaker-- saves alot of time.
It was a weird game in that we had 2 land spawns in the same place-- van and bikes at spawn point #1...