You can do it with the vehicle on the ground too. After undoing the top lock nut, I find it easier to hold a spanner on the top nut, and use a socket wrench on the lower nut. Don't forget to nip up the lock nut afterwards. Put plenty of grease or waxoyl over the nuts ready for next time. Now you have greasy fingers, don't forget the steering stops, two each side, a blob on each will last the winter.
Stops that annoying graunching on full lock.
But bounce it after you have adjusted it to settle it.
These bars do sag after time, so a couple of inches will probably get it back to what it should be. Check clearances on the front rubber bump stops, two each side, but they may have gone walk about.:doh
Have a look at any tyre wear on the front tyres, and make a note and compare it over the next few thousand miles.
If you over lift, you can wear out one side of the tyre, but my guess is, that as it is too low, you are probably wearing out the other side anyhow.
BUT I can't remember which edge wears most due to too much lift.:doh:doh
Hope it helps anyway.