Jang, not on that boat but I am on a 2 day for this weekend. It is very possible to get in that many dives if you watch your bottom times and depth. Typically if the boat leaves the night before, you can splash before breakfast if you are so inclined. Then an hour per dive plus an hour SI while they move to a new location (or stay if the conditions are so good that divers want to do another one there, or so bad everywhere else you have to stay there). Most boats try to give you a variety of locations. Thats 3 dives by lunch, a couple afternoon dives, and a night dive. I have done as many as 8 (with some being shallow and only 30-40 minutes). Most people do 5 or 6 with no problem.
That being said, watch the weather for this weekend. Swells are up, and rain is in the forecast. That is better news for Catalina than it is for the Northern Islands, as there are spots to hide from a west swell at Catalina. I am suppossed to go to SB Island Saturday. Could be a bit bumpy getting there and back for both of us.