Skyarrow,
Look like you are getting some good flakes off that stuff. I am just switching over to flint from glass and I am having trouble with thinning also. Especially with turtle backs (large humps). But I finally had one of those Aha moments. I was running flakes up off the hump, but it really wasn't thinning the piece. The flakes would go all the way to the top of the hump, but the piece would just get smaller and smaller and still have a nice hump. I could see the nice long flakes but could figure out what I was doing wrong. After making many of these nice little round turle humps it finally dawned on me. I was getting what I would call running flakes and not really thinning the piece because I did not have the platform below the center line. Once I realized this and moved the center line and set up a good platform, I was able to then get a flatter flake that actually did some thinning. If you find yourself making little turle backs, maybe this will help.
Keep whacking.... but I am still jealous you have all that material right out your back door! In many ways I wish I had started with rock instead of glass.
