Judging by the photos that Rick sent, it looks like Bishop does a lot more than the center basement X-brace as part of the full package, at least on the 45' rigs.
They install a much larger lower frame rail along the length of the basement along the existing rail, and add diagonal braces between these.
Then the flimsy factory braces in front of the rear wheel is removed and a large bracket is fitted in it's place. I actually added an additional upright brace in this same area when I noticed that the factory brace was cracked, but I didn't include it in the blog post since I didn't realize that this was part of the package. Photos at
2012.02.24 RV Cross Bracing
Then an additional X-brace is added upright in front of the rear axle, and another X-brace upright behind the genset.
Thanks to Rick for the additional information, and the photos of the bracing on his rig. It definitely makes Bishop's $1500 price tag start to look like a really good deal for the amount of time it takes!