If you are quite concerned about your bike's safety, then I don't think carrying two U-Locks is a big deal, but it does help to get the "right" U-Locks.


Because of budget concerns and differing views on how much security is enough or too much, it is hard to ever get unanimous agreement, so I will simply tell you what I would do if I was in your shoes.


Firstly, leaving a quality chain lock at your work place cage, is a great idea.


Now if you still feel the need for two U-Locks, I would get these two:


1. To secure the rear wheel to your frame, Abus Granit X-Plus 54 Mini - 145mm long - Weighs 1.2kg
2. To secure your front wheel & frame to an object, Abus Granit X-Plus 54 - 300mm long - Weighs 1.66kg


Both the above U-Locks require both shackles to be cut in order to open the lock and both of them are very tough locks due to their 13mm hardened steel shackles.


You could replace either one of the above with the 230mm version of the Abus Granit X-Plus 54 that weighs 1.45kg, you just need to decide how much room you need your lock to provide.


Another possible substitute from Abus for either of the above could also be the Abus Bordo Granit X-Plus 6500, it weighs 1.58kg and is almost as secure as the above U-Locks, but much more versatile in your locking options.


Also, with the above U-Locks, don't cheap out and buy any frame holder for them other than the Abus Eazy KF Lock Holder & Abus Clamp for Eazy KF(Please note that this link takes you to the 12mm version, you will need the 13mm version for the above U-Locks).


I tried the cheaper lock holders from Abus and quickly junked them and got the Eazy KF gear and it is so much better.


Now with the above locks, anything lighter will be much weaker and less secure and anything stronger will be significantly heavier.