A lot of people leave the space and still get 501st approval. If you go for EIB and Centurion status here on FISD, then you need to close the gap. I took a piece of abs, joined it to the kidney piece with a shim on the inside and then applied abs paste (mixture of pieces of abs and acetone) and applied it to cover the seam between the new abs and kidney. It'll take alot of sanding but totally worth it with the final results and the no gap looks a lot better.
Here's how to make abs paste if choose to go this route. Take your time with it!
http://www.whitearmor.net/fisd/HOWTO:ABSpaste
Here's what mine ended up looking like