You have to do that much grinding to get the Core 5000 to fit even though it is only .5mm taller than the Orion 4800 and Trakpower 4900, both of which I hear fit with no modification??
My Orion 4800 will fit without grinding but is pushing on the bulkhead and introduces some tweak. When I swap out to a different battery the tweak disappears, so it's definitely the battery. It's not severe, but it's noticeable.