Snuffy,
The reason for the TL design is it is successful. I'm not clear what the magic is? I got hooked on them when I got a six-cavity mold from Lee for their .38 wadcutter TL design. That bullet, fired as-cast, cut group size in half in my K-frame Smith revolver. I then got three of their .45 molds, RN and TC full weight, and the 200 grain SWC. Again, they outshot the other cast bullets I'd been using of the same respective shapes, though not nearly as dramatically as that first experience. And, this is just in two guns, so I don't know how universally true it is? I just know the design does really well for my target guns.
I did get one mold design of my own made by Lee and it worked out fine. This was about three years ago when the backlog wasn't so extreme. I wanted a heavy weight that would fit the .45 ACP, the .45 Colt, and could be paper patched as a light .45-70 bullet. To fit in the short .45 ACP case, it had to have a boattail to get past the part of the case that gets thicker near the head. If I had it to do over I would have increased the radius off the meplat. As it is, it has to be seated a little shorter than I like in order to feed properly in my 1911's, despite their modified feed ramps.
I did not specify the microgrooves, though I drew them from Lee's information sheet on them, Lee knew how to make those themselves. I also made no mold allowance. I told them to use their standard gauge diameter for .45's.
