Neat solution for the original U Lock, however there are much better locks and disc locks on the market now (some 15 years on), that fit under the seat leaving alot of space to spare.
I'm considering cutting away some of this white plastic moulding underneath the seat, as it prevents me fitting some items into this space, without the seat becoming tricky to fit back into place. Specifically stopping at a petrol station for some lunch plus a 500ml can of
Monster - it just wont quite fit under there in any position without getting crushed! Grrrrrr.