Maybe I'm wrong, but I was under the belief you could use a belly up by installing a 1" body lift to get the extra room required to install it. Nth degree makes the "Tummy Tucker"
for the Rubicon, but it takes some work to get it on and it is not cheap, and TeraFlex
makes the Belly up and they state that their 1" body lift is required as well as the engine lift spacers included in the kit, now Tera does not state whether the belly up has issues with installation on a Rubicon, so I don't know about that.
As for the fuel tank skid plate, YES that is a definate, mine is already a little shorter in one spot thanks to the help of a rock, so I will definately be skidding that as well as my oil pan, adding after market control arms, steering box, etc. I plan on doing all skid protection before I do a lift of any kind, then I will add a lift big enough to go to 33"s, thats as big as I plan on going (well at least thats the plan, I have said that before and ended up with 36"s, but for now 33's will be fine for the Rubi)