I don't know how many folks use an ab wheel - I don't recall ever seeing them in videos, but you never know. I use one in the gym sometimes and basically got stuck at the level of kneeling rollouts. I experimented with ways to make them harder - holding extension, for example (torture!), and using a band to make life more difficult - but still felt more or less stuck. Doing a full standing rollout seemed like too big a progression, as I suspected I'd wind up bellyflopping on the gym floor in a spectacular fail which would no doubt wind up on YouTube. Not how I wish to gain notoriety.
However, this past weekend I saw a guy in the gym doing a cool ab wheel trick and struck up a conversation about it. And without futher adieu, here are a couple of progressions you might want to try if you are caught between too easy and face plant:
1) Use an incline surface, such as an incline bench or a ramp. The steeper the incline, the easier it will be to roll out/in. Decrease the incline over time so you can progress to:
2) Start standing, perhaps 4 feet from a wall. Roll out toward the wall. The idea is, the wall will limit your extension - you will only go until the wheel hits that hard surface (so, no face plant!). It's still plenty hard to pull back. Gradually increase your distance from the wall until you are able to do a full roll out. (Or, if you are super tough/have been perhaps using a suspension trainer, you might even be able to start here.)
I tried both yesterday and settled for #1, at a fairly low angle. Today, it hurts to laugh, so the exercise gets two thumbs up from me. Great anti-extension work, no embarrassing video!
Hope that helps someone out.