If you use just sealant on that, your unibody will become messed up. Once you cut past the unibody the integrety of the body will decrease in that area. Weld it up, and your all good. Find a friend who has a welder, or go to a club meeting and ask who would be willing to weld it up for a six pack.
When I did mine, I really had no idea what I was doing. I jumped right in and started cutting. Considering how I did it, I think it turned out really well. I have a 2 door, so its a bit different especially in the front of the fender.
Heres what I started with. Flexed with 4.5'' of lift on 32'' MTRs. Not full flex, but only pic I have.
Rear quarter panels bent up and welded. The back of the fender is started to be cut.
Before I had cut and hammered to the pinch seam. I unbent them to but cut off. You can see the line drawn in the mud where I hoped I would end up.
Heres a pic of it welded halfway. When you start to weld, buff off the outside paint too. I forgot that small little detail and you can see where the paint caught on fire. Opps.
Pics of my awsome welding skill. If I would do it again, I would only do 2 relief cuts per side. I did so many, and it was a pain to weld all of them up.
Finished but unpainted
Painted and all done.
edit: Sorry, my pics got messed up. Hope this helped some.