I have done the Genright sliders to 2 of my Xj's by cutting out the rocker panel and welding the sliders up inside. It is not that big of a pain if you have done it before, my first one turned out ok and was functional but did not look great.the second was far easier and looks great. If you have the time and skill I would totally recommend doing it this way. And I will be doing this to a friends Xj When he gets around to fixing his. let me know if you want some pointers, might even have a few pics some where.
Pook