First you quote me out of context, I said "they don't stretch unless ..." Then you go ahead and make my point.

Assuming the ideal spoke tension is that which brings it to a certain percentage of it's tensile or yield strength, then for all spokes of the same material the elongation under ideal tension will be the same. (see Youngs Modulus) The ideal tension will be proportional to the square of the diameter, so a reduction of 25% in the diameter would call for a reduction in tension of about 44% (.75˛ = .5625). The converse is true, so if you know the tension you need you can select spoke gauges accordingly.

Your problem is that you were overtightening your Revolutions taking them beyond their elastic limits, and stretching them. If used within proper tension ranges DT Revolutions wouldn't be any longer under their ideal spoke tension than any other stainless steel spoke.

Because their smaller section calls for lower tension, Revolutions make an ideal spoke for left rear flanges, especially with lighter rims, solving the problem of an overtight right flange, and undertight left flange on the same wheel.

Now as to which way to round, that depends on the spoke calculation used. Some tend to give you a number at the low end of the correct range, others tend toward the high end. Many builders, like myself, always use the same calculator, and know where the spokes tend to end up w/respect to the tops of the nipples, and therefore know exactly how much room we have to fudge, and in which direction.

To the OP, when this wheel is finished, I suggest you make note of which calculator you used, what the calculated length was, how much you added and subtracted and where you ended up. Calculators are fairly consistent and knowing the above will be valuable next time you build a wheel.

Actually what you said was Spokes don't stretch unless.......

The bolding seems to emphasize that they don't stretch, and of course they do. I did read all of your post and agree with why they stretch. On my wheels I used just enough tension on the drive side so that I could add enough tension to the non-drive side spokes to stop the breaking at the "J" bend due to excess flexure. With the higher tension the spokes stopped breaking but over time Revolutions stretched on the drive side until I ran out of threads. Revolutions are still my favorite spoke, But I no longer use them on the drive side rear.
I know that the stretching problem is not limited to DT Revolutions. As I said above, the spokes on the MAVIC Helium wheels we had (my wife's bike) stretched until the nipples could not be adjusted. This was due to simply trying to maintain true and dish. They were factory built. I believe those spokes were something like straight gauge 1.7 mm, not sure.