Lately I've just trimmed the hammer spur a little with the dremel until flush with the top of the factory extension. If it's still to tall, I trim the front shoulders of the hammer extension so it sit lower on the hammer, then trim the spur flush again. This will get the hammer low enough that the extension will hit the barrel release which is too low and you'll need to use a smaller profile hammer extension or trim the barrel release for more clearance.
Tim
