I finally got my small diameter splined lug nuts on my car.
There was no need to worry about exposed threads, the nuts are longer than the threads of the wheel studs, almost flush with the last thread on the rears and maybe 3 threads past the end of the stud on the fronts.
Without the use of a scale, I estimate the new lug nuts weight about 1/2 of the stock nuts and I saw the small lug nuts described as 25 or 28 grams, right around or just under one ounce, so four ounces lighter per wheel, 1 pound of weight off the whole car.
Its all unsprung and rotational weight (but near the axle centerline so probably not enough moment of inertia to effect acceleration in a measurable way).
Any way, they look fine, are more theft resistant than standard nuts, weigh less and are now torqued to spec with a clicker torque wrench.
The wrench will be a help on the track when changing to race wheels. If I do 12 events a year, that's 24 wheel changes in addition to the maybe 1-2 times for flats, rotation, switching to winters and new tires so there are many more times to screw up your studs or wheels. Controlling the torque and never using an impact wrench are the best way to protect them.