Dave,
Cecil has been doing Leupolds for the stoolshooters for a long time. He changes the spring configuration on the erector tube and a modded Leupold comes back looking somewhat like one of the Burris Posi-Lock units. (In fact, I'm pretty sure that Cecil was doing this before Burris 'discovered' the process.) Unlike the Burris system, however, Cecil's scopes don't have a mechanical lock -- it's all done with spring pressure.
As I understand it, this does not void the Leupold warranty -- although there's a bit of 'gray' area there...
I'm loathe to rip mine off and make a weight comparison
but I'd guess that less than an ounce is about right. Cecil can tell you, I'm sure. For that matter, Theodore had Cecil do one a year or two ago after he and I discussed it. You might want to ask Dan his opinion.
Cecil Tucker 1567 Jude Avenue Odessa, Texas 79763 (915)530-2919 Scope Repair and Modification.
Last I had one done it was $160. (I really don't like spending the money on a Leupold and then having to add another $160 to make it 'right'!)