Tip: Layer 3 backgrounds and tides disappear when you hit a message box, so plan your level around that. For example, you can add a sublevel without layer 3 at the start/midpoint, and include your message there.
Blame erik for not noticing
Thought for sure that thing was included in the original GPS. Dunno if I should update this or include it in GPS' next update though.
Anyway, sorry about that I'll fix it one way or the other.