ORIGINAL: RCKen
You can adjust the tension on your wheels so they don't roll as easily. Put a little bit of fuel tubing in between the wheel collar and the wheel on each wheel of the plane, then push the wheel collar tighter against the tubing to adjust the tension on the wheel. This will help keep the plane from rolling as easy, but you'll still be able to roll for takeoff. This will also help slow the plane after landings. You still want to try and get your idle lower too, but this will help you fix your problem.
Hope this helps
Ken
This works VERY well. But I would add a washer between the tubing and the wheel. Some silicone tubing has DESTROYED my wheels in less than a hundred flights. Adding a washer helps to avoid this.
I know it sounds like it makes no sense, but the metal is far easier on the plastic wheels than soft, plyable silicone tubing. I don't really know the physics of it, but has happened to me. Are there any materials engineers or chemists in the house?