I used one of their Griffith locks 20 or so years ago and it worked fine.
I bought one of their Ketland style flintlocks about 8 years ago and I had to send it back because it was so poorly made.
Five years or so ago I bought one of their so called T. Campbell locks. It was functional but had too many casting pits and I always wished I'd have sent it back too.
The boss there Greg Roberts told me since then that they have the bugs pretty worked out of their locks.
They won't sell you their Gibbons style Hawken lock that comes with the kit, but if you want to try any of their other locks I'd call Greg and ask him to pick out one that functions nicely and has no casting flaws that will show on the finished product, unless you're good with a TIG welder. He is kind and easy to talk to.