Am in the middle of building a TOTW Bivins flintlock. As this kit is set up for the Siler large (Chambers) flint lock, that's what I got. I found the frizzen spring to be somewhat stiff, and the foot a little too unfinished for smooth action. So, that was adjusted.
The real eyeopener was Uncle Waugh's suggestion to change the hammer out for L&R's English Manton - London hammer. The goose neck one. Happily, the square tumbler cuts are identical. Advantages? First, the Manton cock jaw is slightly longer giving a better purchase on the leather bound flint. Second, the Manton jaw is angled just slightly more down than the Siler's. This results in a faster, less "scrapy" strike. Noticeably faster, actually.
If I were building from scratch, I would go with Durs Egg.
