IMO there is no straight one and only answer to your question.

There are a lot of differences between shooters - while one thing may work for one it may be totaly useless for the other. Sight picture that one sees sure falls into this category - there are guys that don't need much of affirmation looking through the sights to decide at what point they are aligned, then there are guys that need much more...therefore the steepness of the V depends entirely on you - while one can be prety happy with shallowest V other needs a deepest notch to see it - Your eyes have it! To see a center of the rear is crutial - therefore if you need to have a sharp angled V so be it - you may sacrifice a bit of speed for accuracy and that's not bad at all - you just need to decide on how much.

I'd pick a .22 and try a couple of different rears with it, after finding the one that suits you best I'd apply the resullt on your double.

P.S. Take your time - Don't take any second bests - it is worth it at the end!