I did test this, and as you suspected, it didn't work since the 7,1 uses a different layout ID. I did a diff between the elcap and sierra kexts and implemented all the stuff removed between the two into the Sierra info.plist, but that didn't change anything. Using the elcap kext on Sierra fails due to a symbol from a debug function used by AppleHDAController being missing in a kext it depends on (I'm not at my iMac right now so I'll have to check what this was later). I was going to try replacing AppleHDAController in the elcap kext with the one from Sierra to try and work around the unresolved symbol, but ran out of time to test.