So you basically measured from the edge of the piston (lowest portion of dome) to the center of the piston (highest portion of dome), height-wise.
You used two measurements, diametrically opposed, and averaged the two accounting for an imperfect level on the bar.
If all you're looking for is the piston dome height from the edge of the piston, it sounds reasonable, probably reasonable enough to use in your program.

BTW, that tiny gap above the ring can easily be as much as the small recess for the spark plug, which is a factor in compression ratios.
The pistons I just replaced in my agcat had .4" between the piston edge and first compression ring, then factor in the 1/8" gap between the piston and cylinder...that's a lot of extra volume!