Do you know where in the nipple those spoke calculators set their target?
If a calc aims for flush with top of nipple, then 2 mm too short will still be OK. 2 mm too long won't leave much margin - if any.
If a calc aims for flush with tool slot, then 2 mm short is supposed to be less than ideal. But 2 mm too long should work.
OTOH you can add a washer under the nipple to increase the ERD on the short side. Kinda counter-productive if you're trying to build as light as possible, but doable.
I'd be a bit wary of an all-1.5 mm build. They're quite stretchy and prone to wind-up. If it's a low-count wheel you might not get the tension needed.
I'll happily use them on the NDS though on most wheels.