Designing a tailpiece

I have the fingerboard pretty much shaped and decided to get working on the tailpiece.
I've made a few and used store bought ones. On the shorter models I've made, store bought are always too long. Since this is a "standard" length Strad at 357 or so the store bought would work. But I have the ebony fingerboard that actually looks like wood so I figured I'd make a matching tailpiece. The first question is how to make it. You could to it empirically, and copy a bought tailpiece. But how do know it is right? I set about to design one from the ground up.

I have two tailpieces sitting around. One a cheap, black (looks like plastic, but isn't) round one, and another rosewood one with the two flat angles on it. They just picture them in the catalog, and don't name them by style, so they are just round and angled. They are both within a mm in length, around 114mm. The length is just right for this violin. The hole spacing, slots, half-round lip that sticks up (I have no idea what they call that), and the outside shape is virtually identical. It looks like the angled one may have slightly lower E and G holes. What would be the implication of that? I had to do some trig. I've figured out string angles before, but didn't get the actual angle. Coming up with those measurements brought some surprises. The D string has the steepest angle, followed by the A. The E string has the flattest angle followed by the G. Lowering the G and E strings at the tailpiece would bring them closer in relationship to the A and D in between them. Doing this the G and E strings aren't technically heading directly to the top of the saddle, but they have to go there anyway because that is where the tailpiece attaches. The A and D are directly in line to the saddle.
On a violin where the simple string angle I measured before is on the steep side... 157 degrees or a little more, having the E and G at flatter angles may be a good idea. The difference I figured between the inside and outside string was about 2.5 degrees. That's more than the difference between models. The 42mm radius on the black tailpiece doesn't seem like it would work at all. That one would flatten the outer two strings over 2 degrees more. Maybe I'm on the wrong track. Maybe I'm just plain wrong. Oh well. I'll make up my "experimental" tailpiece. If it doesn't work, there's always store bought.