These are my current one's I have pics of:
Rev. 4

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Rev. 3

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Rev. 2

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Lemon Block
The pin concept is sound and it simply works. But if you want the best performance then go with a "Cascade" style block. There isn't a Pin style block that will compete with it nor can one be made unless the inpingment of the Cascade is included, but then the pins would be pretty useless.
My Rev. 4 and now my Rev. 5 is as efficent as I can make the Pin concept. I have a DD Maze 4 coming so once I get it and test it and test my blocks against it it will give an idea how good my Pin style blocks are. I am expecting White Water performance, but will settle for kicking the Maze 4's ass.
Now for your design I would say make the pins round or at least diamond shaped. Make the pins 3 times as high as the thickness of the base (after all milling is done). Duel outlets, not a huge gain but it is very evident in my Lemon Block and Rev. 2-5 designs. Base thickness should be around 1.5mm. Don't go much less or the block might collapse for lack of support.
After it is perfected expect about the same results as a TC-4. Might get close to a White Water, but nothing near Cascade performance.