Checking my calliper alignment with a feeler gauge between pad and disc... how much is too much? On one side I can't get the gauge in, on the other I can get the 0.006" gauge in at the top. Worth fettling?

[Edited on 18/4/15 by rodgling]

I don't think I understand the question. Surely the key measurement is between fully retracted piston and disc surface. They should be roughly even and obviously larger than the pad thickness. The gap between released pad after braking and disc is a function of the design of the seal and is designed to be a few thou at most. If the seal is worn then you may get a problem here.

It's really that the pad needs to be square to the disc (or as you say piston needs to be square to the disc - this is just a more practical way of measuring it), it wasn't. I've now shimmed the calliper slightly to get it square, can't say it has made a huge difference though.

unless there is obvious misalignment, don't worry about it, as the brakes bed in they will, well... bed in!

in normal running you only want/need a miniscule gap when the brakes are off, it can happen that the seals can pull pistons too far back, but 6thou would be fine.

edit to add
if you have large gaps disk to pad in normal running, you should also check disk runout, and the wheel baring's

[Edited on 18/4/15 by gremlin1234]

Yeah, pedal travel feels quite good - it was just as part of a general overhaul of the brakes to make them as good as possible I thought I should give it a go.