Its easy to do but are they case hardened?? I havent messed with the lash pads on the l series yet but I know that in a pinch i have taken a piece of glass and some 1000 grit sand paper and sanded down shims for a motorcyle before with good results. You have to have micrometers to do this obvously and you have to keep checking for squareness and to make sure your not wearing one side down more than the other. figure 8's is what ive found to work the best. Also make sure you do it wet.