Thanks for the reply. The larger lip that is parallel with the cutout of the case is pressed up against it tightly. I've pushed against it with a substantial amount of force, but the only movement I'm able to get out of it is the compression of the foam on the shield, and the standoffs are still too far off. I've built many PC's over the years, so I'm not afraid to use force to install a motherboard. I've had some cases that have been an issue that required excessive force to get the first couple of screws started, but the other boards I tried in this case went in with little to no force.
On the shield, the edge that goes towards the back of the motherboard is folded over to the back of the shield, and then is bent again towards the motherboard, parallel to the motherboard. This final bend is roughly 3 or 4 mm. If this lip was over the back of the motherboard, instead of being butted up to the side of it, I think I should be able to install the screws. What I don't know is if it is intended to come that way from the factory. As it sits now, the 3.5mm audio jacks are flush with the shield. Should these protrude out of the shield slightly?