I find it much more important to use a target that matches the reticle in the scope.
This fall, while sighting in my 9.3x62, I shot 3 x 3/4" three shot groups at 100 yards with a Leupold M8-3x. The scope has a duplex cross hair. I use a white square surrounded by 1 1/2" black. When the duplex crosshair is precisely placed dead centre on the white square, you see four little white squares. You will immediately see if the squares are not even, so can reproduce the hold. 30 years ago I could use a 1 1/2" white square, today I use a 3" white square. Seems to produce fine hunting accuracy.
I have a flat top post reticle on a 7x57. For that one, I use a 4" black square with a 1" vertical stripe down the middle. I bring the post up to the bottom of the square - you can see the horizontal white disappear, just as the post "touches". The white stripe is still visible to orient left and right.
I personally find the commercial targets with blaze orange diamonds to be nearly useless for me - I just can not see them clearly enough to get precise alignment.
Especially to work up a load, adjust scope settings so you do not have the group hitting your aiming point! You want the aiming point to remain the same, and not be altered by bullet holes.
Edit: There is also something to be said about "working" your hunting scope during load development. You want it to quit or break at the range, not in the field. If it is a variable power, work it at various settings - does the point of impact change? What does a 300 yard drop of 8" look like? If it is a duplex, what is the point of impact of the tip of the lower thicker portion - is that a pre-set point of aim for 325 or 400? At 3 power or at 7 power? Finn Aargaard's 2.5x Weaver is still ticking today after 1,000's of rounds of 375 H&H. Is your hunting scope holding up?