Another +1 for King Cages - hold the bottles super securely, don't mark like AL cages and tension strength can be adjusted by bending slightly unlike carbon or plastic cages. Never lost a bottle under the DT.

I rarely need 3 bottles - so I purchased Fabric Cageless Keg and use it on the downtube. If I am touring and need to mount another bottle, I swap out the Keg (put it in the bag) and use a Fabric cageless bottle. All pretty cheap and keeps the bike looking clean.