I usually use a test kit to test the water parameters of the tank and the water in the bag before dripping as well. If the ph is too low in the bag, as in the 5's, I set the drip really low. If it's set too fast, the pH will rise quick and any ammonia present on the bag water will become toxic to the fish. To help with this, I use a separate siphon to a separate container, so I have the drip from the tank to the bag and another from the bag to a smaller another bucket, Sort of like an automatic water changer. This will gradually replace the water in the bag with tank water and eliminate enough of the bag water to eliminate enough of the ammonia toxicity factor.
On the other hand, in the rare instance that the water parameters are just about equal, I'll float the bag for temperature and then drop the ray in.