Two phones for one Extension - BLF Fields

[TSlocum]

We've got Cisco SPA-514g phones and 500DS sidecars. When I provision an extension with two phones, one phone has a sidecar and the other doesn't. When I set up the second phone, it copies the BLF from the first one. If I remove the BLF from the second phone, it clears it from the first. How can I provision these where one is a SPA514g + 500DS, and the other is just the SPA-514g without BLF settings?