You can simply rename the RAWX86's kernel to, say, RAW, before putting it at the root of your Lion system. Doing that, you won't need to replace the older one (that's named mach_kernel) and will be able to use it if the things go wrong and RAWX86's kernel doesn't work with your current 10.7.2 installation.

If you do as i advised, just remember to boot using the name you gave to the kernel as a boot flag. If you call it RAW, just type RAW and, just for safety, npci=0x3000 and hit enter. If you want to boot with your older kernel, just doesn't type anything.