IMO, you've basically plateaued at a level of bump skiing with your current skillset.
I understand your addiction to bump skiing, it's challenging, super fun and usually uncrowded.
Over time, you may up your speed a bit, but you'll never advance to another level unless you learn how to load your shovel edges to initiate quick turns.
Without developing this skill on the groomed, you'll always allow the mountain to dictate where you turn and the timing of the turn finish, the terrain below you will drive the bus.
If you were to change your skiing pattern to say 25% of each session working on your quick carved turns (brushed carved turns) on the edge of the steepest groomed you can find, over time, you'll be able to bank or deflect off the bottom side wall of the mogul instead of skidding sideways into the bottom of it.
Down the zipperline, you'll be able to carry more speed comfortably down low angle bumps, on steeper terrain, since you'll be deflecting off the side wall of the mogul and not skidding into it, you'll be looking for more speed control, since there are really only 2 ways to dump speed down the zipperline. They are either skidding or slamming or a combination of both. This is because when confined to the zipperline, there usually isn't enough space to actually complete a quick carved turn which dumps speed as the tails brush at the the turn finish. The ski tails hit the base of the mogul or bottom of the trough before they actually get towards 90 degrees to the fall line.
This is what TDK is getting at with the purple shaded moguls. If you were to develop a solid quick carved turn, you never have to "look" for a zipperline or skid sideways into the bottom of a trough again to gain speed control. Just turn, turn, turn. When you turn into, through and over the purple shaded areas, there is almost always ample space that allows you to "complete" a quick carved turn where you dump speed by consistent brushing at the turn finish, no more skidding or slamming for speed control.
So it's up to you, either develop a solid quick carved turn on the edge of the groomed which is initiated by shovel edge pressure or be willing to take the increased impacts required to gain speed control if you continue to pivot and skid while upping your speed down the zipperline.
Choices...but this investment of time pays huge dividends.
Hooked up at the turn finish, no zipperline, no impact, not skidding down to or waiting for any terrain below me. Just turning. I'm driving the bus and so can you.
Edited by Nailbender - 12/21/14 at 6:38pm