To write the SMC, you only need the first block (0).
Xellous needs only the first 2 MB of a xell/xellous exploit image
So to inject the patched and re-encrypted smc and keyvault into the jasper_6723_hack_256MB_512MB.bin and then back onto the 360 via lpt the commands would be:
nandpro jasper_6723_hack_256MB_512MB.bin: -w512 kv.bin 1 1
nandpro jasper_6723_hack_256MB_512MB.bin: -w512 SMC_enc.bin 0
nandpro lpt: -w512 jasper_6723_hack_256MB_512MB.bin
and this would allow me to boot into xell using the AUD_CLAMP solder point after flashing.
I ended up just soldering the wire back to rf point and reflashing jasper_6723_hack_256MB_512MB.bin then updated xell to xellous. Then I rebuilt the freeboot with AUD_CLAMP smc patch again and udated through xellous then powered down and moved the wire back to the AUD_CLAMP. Powered on and it was right.
I must had stuffed up the last image file and it wasn't working then. But all is fine now so thanks.