Personally, I would carry a front. Front would probably work on the rear better that rear on the front and the front is also a little lighter, smaller and easier to carry.
Edit: I have an R and a front will go on the rear (but reduces the inside clearance a little) but noticed you have an X. The X has different rear suspension so I am not sure if a front wheel will clear on the rear. You will need to try before you buy.