Stiks, this is
theoretical from a calculator that I use for long bows. Have used this on three new builds and have hit within two pounds on all of them. Here's what it spits out:
NTN 66"
Riser length 18"
Limb width 1.5"
string follow .75"
Stack .404
To go to a 1.25 inch width, increase stack to .429
Limbs with a gradual taper to 3/8" wide tips at the string nocks.
I know that the "gradual taper" kinda leaves you hanging a bit, but all three that I did off the calculator had slightly different profiles without significant impact on weight.
I sure don't guarantee that his formula will get you there exactly, but I'd say that if the NTN length is not absolutely critical, startt with a 69" NTN and go gradually to desired weight.
Would be smart to listen to and consider as many opinions as you can get!!