I havn't personally installed a powertrax system in my jeep... However, my dana 30 doesn't have clips... Upon taking the wheelbearing/hub off, my axle pulls strait out of the carrier. If you look at how the axle assembly is put together, there is no way the axle is going anywhere BECAUSE of the fact you have a hub assymbly...
Now, if you wern't a 4wd vehicle, or if we were talking about the rear (excluding non-clip axles) then you WOULD need C-clips because there is nothing there to gold the axle into the differential... Meaning your axle, drum, and tire would take off into the woods and leave you sitting on 3 or less tires lol. Simply put, your wheel bearing/hub assymbly is responsible for keeping the axle firmly seated inside the carrier spline.
Personally, if it were me, I would install without and store them for safe keeping just in case... But as stated before, I have a Cherokee one piece conversion and neither the cherokee, my stock, nor the drivers side axles had a c-clip on them.