My son has trouble twisting the grip-shift on his MTB (he's 7) and tends to leave it in a low gear to avoid shifting. I lubricated the derailer and made sure the cable was in good shape but it had no effect. I even took it to my LBS and they essentially checked the same things. Then I noticed on eBay an Avid Rollamajig and it appears to be the answer to the problem but was curious as to why such a seemingly perfect device is no longer made? Anyone have experience with this item?