I just received my new chest freezer and had to mod it a bit, but it works! I use blichmann 7gal conicals and the freezer is a Danby DCF550W1 5.5 cu.ft. Chest Freezer. If you're scouting a similar solution i'd try to find one that was a few inches taller, though I had a tough time. 5 cubic feet will be plenty pretty much whatever dimensions as long as you have enough height.
pics attached. The second one shows the little bit I had to dig out of the top insulation to get it to close over the blichmann's pressure weight and blowoff.
Sorry if this post seems obvious, but I didn't find a lot of pics and reference stuff out there for people lagering with these conicals so I figured I'd share it.