Something worth mentioning is the efficiency of today's skimmers. 20 years ago skimmer technology was not even close to what it is today, and that is when the recommendation for getting a skimmer that was rated for twice your tank volume was established. However, with today's skimmers it's just not that cut and dry. Sure, that may get you close, but it may also get you more skimmer than you need. 20 years ago I wouldn't have thought anything of putting a Berlin skimmer rated for 200gal on a 75 or even 55. However, I wouldn't dream of putting a SRO-2000 on a 55 or 75 unless I was planning to pack it with a very high bioload. Comparing today's skimmers and skimmers from 20 years ago is pretty much like apples and oranges, so advising on skimmer size needs to adapt accordingly.
When I first started my 220gal, I intended to make it a FOWLR tank and therefore I purchased a SRO-3000INT. Well, the FOWLR idea didn't last long as the first few fish that went in were reef safe, and I upgraded my lighting to LEDs. At that point a FOWLR seemed pointless but the 3000 seemed like too much skimmer for a softie tank. So, today my reef is 95% SPS with a handful of LPS and a light-medium bioload, and the skimmer performs beautifully. I personally am a big fan of how Coralvue rates the Reef Octopus skimmers. They do give a general recommendation for tank size, but they also give recommendations for tank size based on bioload and tank type. IMO, that is the key to getting the proper skimmer for your tank. I personally like to balance it out so that I'm not having to replace a lot of minerals in my tank. Yes, I do dose, but I dose a normal dosage on everything simply because I'm not pulling a lot of extra out of my water.