Only thing I ever add to the stock is a slip of paper, with my name, address, phone number, and date of purchase. Hopeful that it could aid in recovery if the gun ended up stolen.
I've seen Darnes with broken toes on the stock, actually, lots of guns, not just Darnes, but, I think the stock is more than strong enough to be used when they are hollowed. The hollow begins way past the attachment point for the action. Both of my 12s are solid, now, my little 12 was hollow when I got it, but, wears a solid stock now. It was restocked in France. The second 12 may be going that route as well.
The cresent is normal-the factory buttplates are shaped like that.
Let us know how it shoots.
Best,
Ted