My understanding is that this is actually really complicated to pull off without trial and error. I know that F360 has some tools specifically for this (and requires specifying materials, acceptable radius, and so forth), but otherwise I think this probably requires some experiments to see what’s acceptable and what isn’t.
I typically use a “K factor” to calculate my developed length. This factor is dependent on material type, bending style, and radius of bend. Here is a good article describing this K-factor.
For example: For mild steel, I start with a K-factor of 0.375, up to a 0.5" inside radius using an air bending style. For a bottom bending style, the K-factor goes to about 0.4 to 0.45, and for coining, a 0.5 K-factor usually gives good results.
Unless you are trying to hold +/-0.005" for your bend lengths, I would just use a 0.5 K factor.
You need to have a general idea of your radius, and I’m assuming you will be bending these by hand?
As far your V cut, what you have looks great. The little radius you have at the bottom of your V is a bend relief, this needs to be about 1/2" of your material thickness for the diameter.
Here is a quick Solidworks model showing the relief in the corner: