cpq summoning

Ok, I have being doing cpq on my dit lately and when I do room 3/4 I'm fine, but when we do room 5/6 we almost always lose. Most of the time my team is winning my 100-150 points with like 4-5 minutes left, then once both teams start to summon monsters and buffs, my team always ends up losing. I go with different parties almost every time, so people are summoning differently, its not like we are doing the same summon every cpq and still wondering why we lose. So I guess my question is, what do you summon and when? And is your team leading when you start the summon and do you keep the lead?