--How does one go about improving the long, mushy trigger pull on these??? I've done ARs and Garands and '03 Springfields, but the double-hook geometry escapes me. What surfaces benefit most from stoning???

Here's a picture showing where I removed metal from mine. This causes the disconnector to pivot further forward. When you pull the trigger the disconnector will then bump against the hammer. It gives it a two-stage feel. File, test fit.....file, test fit..... it was a slow process.

This is an excellent mod.  I do it to all of mine.

It certainly looks useful-- but I was hoping for some info on how to get rid of at least some of that mile-long creep and the mushy release I now have on all the rifles I've put these into. Guess I'll have to designate a guinea-pig rifle and start experimenting--

The long take-up is part of the design and really shouldn’t be changed much.  A common mistake is to shorten the length of the primary hook in an attempt to shorten the trigger pull.  This can come to no good.  Amoung other things it creates the possibity for the trigger hook to not catch the hammer when it is released by the disconnector.  The rifle would then fire unexpectedly.  The purpose of the disconnector is to hold the hammer back until the trigger hook is in position to snag the hammer as the trigger is released after a shot.

The best thing to do is to turn it into a double stage trigger.  You can make the first stage as smooth as a babies bottom if you polish the rubbing surface on the hammer.  Polishing the hook is not usually needed.  On a microscopic scale, the rubbing part of the hammer surface is very bumpy as it comes from the factory.  Once you get the surface flattened, the pull will be smooth.  I use a small diamond file and always work back and forth in the direction of the hook travel.  You will need to take off a tiny bit of the surface, but that is OK.  Just don’t change any angles or round off the edges.  Once you have that done, the purpose of the mod pictured above is to give a well-defined let off point.  When set up right, the disconnector will contact the hammer just before the trigger hook releases the hammer.  The contact with the disconnector hook provides resistance at the let off point.  As this resistance is overcome, the trigger will feel like it snapped all at once.  These make very nice two stage triggers once you do these mods.  Hope this helps.

P.S.  Go easy on the disconnector mod.  If you go too far, the disconnector will never release.  Then you will have to take some off the disconnector hook or the back edge of the hammer where the disconnector holds it.   You might want to experiment on a scrap FCG until you get the feel of how much to take off.

I was told not to mess with that part of the disconnector or you may get slam fires.

If you mess it up, you may get slam fires (Don’t ask how I know).  If you do it right, you will get a great trigger.  I only provide this information because I know that people like me are likely to experiment anyway.  I figure that it is better that new experimenters have the benefit of my experience than learn the hard way.  I have not blown any guns up (yet), but I have had a few doubles, even after I thought I knew what I was doing.  If you cant accept that type of risk, better not tinker.  I would definitely recommend not tinkering if you don’t have a private place to try out your experiments.  

Quoted: --How does one go about improving the long, mushy trigger pull on these??? I've done ARs and Garands and '03 Springfields, but the double-hook geometry escapes me. What surfaces benefit most from stoning???

For a smoother pull and not gritty feel:   Take a dremmel with polishing paste,  Polish up the inside contact surfaces of the hooks and the corresponding contact areas of the hammer.   They will shine like fine silverware.

The pull will be very smooth and the pull weight reduced big time.  If you work the dremmel too much and remove metal the pull may be TOO light.   THROW THE FCG away, don't HAVE A SAFETY ISSUE.  You MUST BE 100% comfortable with the pull weight.  If it's too light then you creating a danger to yourself and to others.    Yes, I am a 'safety nut'.