Just to experiment, I installed an x-ray mod into a mod pack, however, I could never get it working. I even tried a "vanilla" profile with only forge and the xray mod installed and it still would not work. Using the normal Minecraft client/w forge, the xray mod performed flawlessly so I know it has nothing to do with the mod. While I understand that many people consider such mods as cheating, I don't think it is up to the developer's of the Curse Client to filter out these mods on a SSP world and that MSP should be left to the server administrator. If the Curse Client is going to filter out mods, then this speaks poorly to the freedom both players and modpack developers have enjoyed in creating and playing this game.