I always use a similar tactic, all my survey vessels will reduce to at least half speed when entering a new system so that they do not suddenly alert any potential npr vessels that I do not know about. In addition when my shipyards are bigger I switch to a carrier style of surveying, this way the survey craft can zip about the system at speeds far faster then the old designs, while giving off far smaller signatures. Meanwhile the carrier craf will make its way at 1/4 or less to a body such as a lone gas giant and then shut down engines until the survey craft complete their work. This way if anything does happen to go bad the large and expensive (I found jump engines to be the most expensive thing to let go boom) vessel can still make a run for safety.
Yes usually once the first fleet carriers come out, my existing surveyors get overhauled and sent out to "secured" systems. The carriers head forward it some gravsurvey fighters with tiny sigs. Theres also usually some geosurvey ones too, to check gas giants in system so a few tankers can move up and get ready. Most geosurvey is still carried out by 4000t surveyors, but new systems get entered by military ships.
Also especially nice how close you can get a 120-150t fighter with a size 1 passive scanner to other ships before they notice.