One trick I’ve used a couple times for long crystals (like tourmalines, beryls, or even quartzes) is to dop the entire crystal, then cut the pavilion and girdle onto one end. Dop the new pavilion as you would for a transfer, but instead of breaking the first dop bond, saw the stone in half! Be careful that you don’t vibrate your stone so bad that the dop bonds break.
Now you have two dopped crystals with the exact same girdle size. On one, your pavilion is already cut and transferred. On the other, you have your set girdle size, so just cut the pavilion tiers and transfer that one too. Obviously the crowns follow.
Use a cutting diagram or write down the angles you use. Assuming you’re using a meetpoint design (as opposed to an emerald or other cut where your tiers float), about the only possible variation is if you cut your girdles to radically different width. And you’ll have a (near-) perfect match for color, since they came from the same crystal. I say “near” perfect because if you’re working with a zoned stone like a bicolor tourmaline, I can’t help you when one turns out green and the other red hahaha.
–Eric