Problems going through the roof

I'm playing round with using llMoveToTarget() in a hud to blast myself around a sim -- the same principle as the Carnival Ticket at the old Carnival of Doom (at least I imagine that's how you ended up in hell after getting killed falling off a ride).

I've tried a variety of methods based on Ezian Ecksol's camjumper http://wiki.secondlife.com/wiki/User:Ezian_Ecksol (feeding the hud the target destination with a chat command when I collide with a trap rather than using my camera position) and, while I can reliably blast myself from one corner of a sim to the other on the level, passing through buildings and mountains with no difficulty, I find it's very unpredictable when I'm travelling straight up -- sometimes I can pass through the roof and go up a couple of thousand meters and sometimes i just get stuck in the ceiling. But try as I may, I can't reliably go through the floor of a skybox to reach my destination.

Inspired by Jesse Barnett's High Altitude Rezzer, http://wiki.secondlife.com/wiki/High_Altitude_Rezzer, I've tried giving myself an additional shove upwards using llApplyImpulse() in the not_at_target event, and this helps a bit but is still pretty unpredictable. These particular experiments have been with target directly above me, so I'm not having to worry about lateral movement interfering with stuff.

I assume SL's gravity has something to do with it, but I can't see quite what. I've tried it with and without flight assists (fight assists certainly interfere). Am I missing something? Or should I conclude this method of faking tps is too unreliable for predominantly vertical movement if there are obstructions, and concentrate on having targets on the same altitude?

Roughly, you want to get enough velocity that you can move through the biggest obstacle in less than 1/45 of a second with as fat a margin as you can muster, to cheat Havok. Then you need to figure out how to slow yourself down and correct course when you get near sim crossings You may find it easier to use a moderate boost at first, and save the big pushes for when you actually get stuck.

I seem to recall a discussion about this when Havok 4 was introduced. The statement was something like: "the physical type of teleporting throuhg objects would be limited or impossible in Havok 4". This would be related to what you see, but not explain the difference between vertical and horizontal moves

Havok 4 made it more work to get avatars through objects, but it still works it you're determined. Vertical is harder, and down is harder than up, but it can be done.