Xenon, I might be able to help you with the green gem combo in part 1 of SBTC with some tips... triggering the launching glitch is actually about the camera position for a big part. I don't know which way you face when you walk into the corner of the wall there, but it is important where you are facing. If you strafe there, you'll most likely face the cannon, but that view is too far to the right. You have to stand before the corner with an angle of about 45 degrees, but slightly to the left I think. What I do then is press the forward button, then repeatedly go from left to right at the same time. It takes some practice, but I'm sure you'll be able to trigger it more quickly in the future as you do it more often. When you get launched high enough you can lock onto the cannon and helicopter down while avoiding the gems. When you're sure there are two fish at the backside of the ship, you can start the combo. I have a tip for this too: Strafe to keep the lock onto the cannon. Jump backwards and get the first two gems. Then jump backwards again while getting the next gems, and activate your helicopter meanwhile. Shoot the cannon twice while helicoptering, then drop and get the rest of the gems, then run to the green gem area, and get the two yellow gems first, then the green one (that's straightforward). You know, the combo with all those yellow gems is much harder, because the time span to get the yellow gem in combo after the gems on the netting, is VERY VERY VERY small, whereas the green combo has no real difficulty to it once you get on the upper deck with the Lockjaw soon enough.
I'm wondering, how much did you score in the netting combo? If you fail to combo many fish with ALL the yellow gems, like I just mentioned, you do lose a lot of points, and that's where those 2000 points lie. It should be well doable to get 19000 if you succeed both combos (I got a netting combo of slightly above 3000 when I got 19200 in the part).
I'm just playing part 2 through everytime now, even if I fail a combo. I want to get good at it. I found that for the first Scaffolding combo, it's actually possible to get a lock on the Hoodblaster and beat him from down below, just like the Hoodmonger Officer! Though it's harder to get a lock onto him, and the shot doesn't always hit. I did find out it's possible. Though it probably doesn't improve much at all, since when you beat the Hoodblaster, the Hoodboom appears, and if you try to get to the Lockjaw first using the Throttle copter, you fly over the Hoodboom and you most likely make him kill himself, so it doesn't really matter anyway.
And the circular arena combo is still annoying. You know, sometimes the Hoodblaster immediately gets on a balloon and moves to the other side as you shoot him, and sometimes he waits a really long time before he does so. Sometimes he does it somewhere in between, and THAT situation is perfect for the combo. If he arrives too soon, the following problem occurs: When I electrocute the second Hoodmonger, he comes in at EXACTLY the place where I'm doing it, and it often results in me killing him immediately after the Hoodmonger, if I accidentally shoot once too much. And that may not happen, because then the Matuvu is omitted from the combo...
Then, if the Hoodblaster arrives too late, I can't combo him after the Matuvu because he isn't walking nearby. What an annoying combo. It's the one that fails most for me, even though I haven't completely managed the first scaffolding combo yet either. And I can't make the jump to the balloons in time in the third combo, so I leave all those fricking yellow gems out of the combo and just kill the Hoodlums immediately. Who cares. And the second combo I managed once so far. The only one I've managed actually, aside from the secret area combo! At least I ALMOST managed the fourth combo, and the third one is easy now that I can leave out the gems. Go me.
Oh and nice idea for the netting combo actually MandM, I used to collect the yellow gems kinda differently, but I have a better idea about it now so I'll replay part 1 a few times. I do it to relax from part 2 anyway, I think part 1 is actually pretty funny to do. Oh and you can also make a second wave start to appear if you shoot the cannons ALL slowly in a way that you only barely continue the combo. That way you can let some new fish appear already, and then you could collect those yellow gems, starting with the first one and then going to the one nearest to the front cannon, that would be better to combo the new wave with. If you can combo all the gems plus two entire waves, the combo will actually be much more than 4000. I will definitely try it out later.