Well when he was fighting at 130 and 135 his fight night weight was around 144-5. Plus, if Ariza is believed then he has to consume ridiculous amounts of protein to stay around the 150 mark, so it may well be possible.
Yeah I'd say he could if he really wanted to. One of the main factors he's been so successful against bigger guys is because they've all underated his speed and power. According to the latest 24/7 (not that it's much of a fact), Pacquiao's training at about 144 currently and plans to go into the fight at about 146/147. Ariza wanted him to be at 151 like he was for the Clottey fight but apparently Manny's not happy with his speed as he tries to move up in weight. It's another reason Pacquiao's been so devestating recently, he fights at a natural weight. All the guys he's fought struggle to get to a ridiculously low weight so they're not fighting normally and they'll lose speed and power. It's not 'PEDs' as some people put it, it's just common sense. Last weekend we saw Allan Green and Glen Johnson both stupidly struggle and lost about a stone just to make a pointless weigh in. For this reason the quality of the fight was a lot lower than it would've been had the fight just been at 175 lbs for example. It's one of the reasons Manny's fights with Margarito should be so easy. Did anyone see Tony weighing himself at the end of 24/7? He may have been 155 or something but how veiny and drained were the guys feet and legs? That'll show up in the ring in a couple of weeks time when Manny rips him to pieces quicker than Mosley did.