My favorite of those you listed is the dolphin tank/seat. That said, I am one of those people who had some issues, which I haven't really written about...
I actually received the dolphin set, done in fiberglass, after a 2 1/2 - month wait. When I discovered that none of the detailed measurements I gave seemed to have been used, and I could not use the tank/seat/battery box combo on my bike, I contacted BCR. There was really no explanation offered for why the parts would not fit. They said I could either send it back for a full refund (return shipping at my expense), or they could fix it, but since they were so busy, it would be another 8 weeks! I figured after paying $1000+ and waiting so long it should have been fixed right away. It left a bad taste in my mouth, so I moved on.
I ended up ordering a custom tank and seat from Sean at Roccity Cafe. I originally wanted the metal armadillo tank from BCR, and what I got from Roccity Cafe looked a lot more like it. He worked with me all the way through, making changes in the design at my request. Plus, the tank and seat were probably 10 lbs lighter than the BCR fiberglass design.
Granted, if you've got a 750, there's probably less chance of error since I bet they build more of those. For my cb400f, the only thing I can figure is that their jig was based on a 400 twin, rather than a four, and they just didn't check my measurements to be sure. who knows... Hopefully they have cleared things up in the customer service department--their bikes and tank designs are truly awe-inspiring!
I do recommend that you contact Roccity though. He can build more than just the CR-style race tank.