I have survey support carriers and tenders, but since survey ships have to fly very long distances anyway, I generally do not embark them. The survey support is for repairs and for carrying scouts, and jump point surveillance pods. And the tenders act as mobile mini jump gates.
I have found that around 800 tons is a good size for a survey boat. Fighters are generally too crapped, not enough room for fuel, engineering, crew endurance and a good engine. And at 800 tons, having more than 4 of them they do not survey very efficiently. 6 is really the absolute largest number of grav survey boats I would have in a single system survey.
5000 ton hangar capacity is simply larger than a single system survey is ever going to need. Unless you are playing with reduced survey points or something, so that it takes a lot longer to survey.
I put scouts, which have boosted engines, and recon satellites, which have no engines, in the hangar, but the rest of the survey fleet just flies on its own.