Finally got Sierra installed. Some problems of my own making some not. Couldn't get the update to work with dual boot (Windows 1st partition), getting the error "unable to unmount or repair", this has been reported by other users - I might try again now I have sorted out other problems.
Make sure you have the latest config.plist version, the current KextsToPatch settings are essential for booting Sierra, without which I was receiving KP's during startup.
During the first installation reboot I needed to select "Without Caches" AND "Inject Kexts".
I also uninstalled anything that might be loaded during boot (before I discovered my out of date config.plist), so removed Karabiner, RDM and a few others. This may have been unnecessary.
Most things seem to be working (though only just started using it, so we will see).
One error rebuilding caches:
#sudo touch /System/Library/Extensions && sudo kextcache -u /
<snip>
kext-dev-mode allowing invalid signature -67054 0xFFFFFFFFFFFEFA12 for kext AppleHDA.kext
KernelCache ID: 3B573CAFED62A711CF63BD2BB6A07D6E
symlink("/System/Library/PrelinkedKernels/prelinkedkernel", "/System/Library/Caches/com.apple.kext.caches/Startup/kernelcache") failed 17 (File exists) <createPrelinkedKernel 2795>
</snip>
Can't remember seeing this before?
Sleep straight to black screen and doesn't wake, I believe this is known.
Will play some more and see what else doesn't work!
Edit: Also I used Clover 3726 as it currently appears to have the greater success rate