I've used my Bushmaster case from Maryland to Oregon as check on luggage 3 times now, no problems. That's the older case w/out the molded-in logo.
My buddy uses a Casey-Birch (?) black pen for touchups. Doesn't match exactly, but works well enough.
The stock sling is worth $2 and you'll be happier with a Turner leather sling for competition, or a nice tactical sling for tac use.
The 10 rounds mags are routinely critized. You've got a decent number of 30s, you need to buy some 20s now, better for prone and bench shooting.
Yeah, you have to take the optics off to effectively put it in the case. You can also try seperating the upper and lower and rearranging things that way.