Certainly a convex face is allowed but I can't see what would make it non-conforming.
Orange Whip Putting Wand legal club? - Page 2
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Honestly? I don't worry much about the details. The shaft looks a bit odd with what looks like some sort of length adjustment near the putter head. I also don't like the convex faces, although I don't know if they are disallowed. I know that concave faces are not allowed. There are so many odd looking putters that I wouldn't go on appearance alone. The fact that every source I could find said that this one was nonconforming was enough for me.
I don't carry training equipment with me on the course, so I just don't worry about the details of club design. I buy and use clubs which are certified as conforming, and what few training aids I use are never kept in my bag. The only training club I ever owned was a heavy 8 iron, which would have been conforming if it had a standard grip. It did not, so it was kept either in the garage or in the trunk of my car, but was never put in my bag.
That is for sure!!
Isn't it amazing what they will come up with to replace good old fashioned technique and practice? Learn what is right, then practice that to hone it with the putter you plan to use on the course. Seems to me that practicing by hitting balls with a rubber putter would totally screw up your pace control. And with the convex face, you don't know if the miss is from poor alignment or poor contact. It's questions like these which I use to justify not spending my money on so-called "training aids".
I've got the best putting training aids available in my bag already - Putter and golf ball, then add my brain to them and mix thoroughly.