You may want to push the 505 a little to the right.
Fit it good and snug against the outer (bungee side) loops so that they hold it tightly. The lower left loop should then have enough slack so that you can press it a little flatter. It should not lift up the leather behind the 505 quite so much then.
I found my bungee and button lined up perfectly - you may have to query yours with Oberon.
The bowing of the sides of the cover is merely due to the leather being new and stiff. It does soften a little over the first few weeks of use and lies flatter. I find that the only bend visible on my cover now is about the outside few cm of the outer corners.