mur:
Wad file sharing is forbidden, as it contains nintendo's code.
only the installer can be linked on gbatemp.
You can use modmii if you want to download the wad files with manual slot selection.
If you use the official installer, it will replace your slot 249 and 250, so be careful and reinstall d2x after that.
You don't choose where the IOS are installed in the wad manager, the destination is encoded inside the wad file.
if you want to change the install slot, you need to edit the wad file with a wad editor on computer (for example ShowMiiWads), or just use modmii to choose the right slot before downloading the wad.
There's still an issue with USBLoaderGX I couldn't fix :
if you use old cIOS rev17-21, the EmuNAND randomly doesn't work if you put it on the root of SD card.
It works fine on root of USB.