In my current remodel the living room and the hallway ceilings are stippled and they have been painted. The stipple job is not very good. Any recommendations on how to remove the stippling off of the ceiling without replacing the ceiling drywall which has blown in insulation above it.

See how the stipples react to moisture - wet the stipples with a spray bottle/sponge, wait a few minutes and then attempt to scrape off. I'd start off with a simple, cheap experiment.

Since they have been painted, this approach might not work.

Get a 2 gallon pump up yard sprayer and wet them down and see if you can scrape it down to the sheet rock. You may have to use an orbital sander to take the top off so the water will soak through the paint.

If that doesn't work, the orbital sander will take it down but it is a slow, dirty process.

Yup - what Mike & Robin said.

Extra screws can help it avoid sagging. Might do 3/8 though.

You should have asbestos testing done on the ceiling covering materials. Several samples and testing should only cost $100-$150.

If there is no asbestos, they you can try to remove a small section to see if the "water" method will work or if you'll need to do some heavy scraping.

In one case I used a wet and dry continual HEAP vacuum and used a sprayer with a scraper hose attachment and was easily able to remove most of the ceiling finishing.

Another case the material had oil based paint and primer and water did nothing. To scrap would have taken forever. So I had three choices:

A) apply a smooth coat of light weight plaster over the ceiling

B) install a 1/4" drywall over the current ceiling.

C) remove and replace the ceiling with new 5/8" fire core drywall.