Hi robbertwilliams, thanks for the update.
Believe that you have read the Article noted previously:
"Here is a good Article on measuring SGs, from Surrette Battery. The SG for fully-charged batteries is one difference between the Chart in this article, verses your battery SGs:http://support.rollsbattery.com/support/solutions/articles/4347-measuring-specific-gravity
Personally, would draw two samples and expel them, then draw the third sample and use that for measurement.
Keep the Hydrometer vertical (plumb) while taking the readings.
I did buy three Hydrovolts, a few years ago, when MidNite began distribution of this Hydrometer. I got relatively large variations on successive draws on a given cell. Sometimes the scales would stick together, requiring a rap on the top of the battery case to cause the scales to move. This, plus the very short sample tube made the Hydrovolt relatively difficult to use, and the readings (to me) a bit suspect. So reverted to the tried-and-true Freas Glassworks Hydro, which has very repeatable readings. The issue with the Hydrovolt's short sample tube probably is probably only an issue on batteries with a large electrolyte reserve (space above plates for electrolyte).
It is very, very important to rinse any Hydrometer three or four times after a measuring session, using Distilled Water.
A Hydrometer should give very repeatable readings on successive sample draws beyond the third draw -- only one or two points variation.
New batteries usually need to be cycled 30 - 70-ish cycles before they stabilize. So variations in SG readings could be seen, as the battery becomes "finished".
A variation of 10 points or so, for a fully-charged battery should be fine. Many manufacturers suggest an EQ for variations of about 20, or more SG points.
You appear to be using an SG of 1.265 as fully-charged. If so, did this information come from Deka?
The SOC reading that is determined by the Classic using the WBjr, is only a rough indication of actual SOC. There are many variables that go into calculating SOC, and most battery monitoring devices cannot keep track of all of these, and we users of batteries would not know what values to enter, if the monitor had the ability to keep track of all of the variables.
My CC makes all of its decisions on charging, while ignoring the stated SOC data.