Here are some discussions and George Post's "Shake it Up". You'll have to read down through the discussions to find it. Surprisingly George got better results with plastic reels and tanks. These discussions come from Mike Johnstons "The Online Photographer":
"...what is the best way to agitate film?"
George got the best results developing one roll of film in a two-reel Paterson plastic tank, the kind with the plastic reels; he left the other (empty) reel in the tank and used half as much solution as recommended, to leave a sizable airspace.
Second best results were achieved with a stainless tank and stainless reels, also using an airspace and leaving an empty reel.
For many years, adapted from his results, I developed 35mm Tri-X 400 three rolls at a time in a 32-oz., 4-reel tank, using 28 oz. of D-76 1:1 (my handle on certain forums is "txind76121"), leaving the fourth reel present but empty.
George's key findings--I'm just going on memory, I haven't seen the article in years--were that plastic reels and tanks were better than stainless and that it was always better to leave an airspace.
He also advocated agitation by inversion, as most writers do.
I believe he also advocated continuous agitation. I might be wrong about that. In any event continuous agitation is impractical for most users because it results in too-short development times.
I do have a copy of the article somewhere, but the chances of my being able to put my hands on it are very slim
I remember reading the article Mike is referring to. He has summarized it quite well. The only thing I would add is that Post recommended using a spacer if necessary to keep the reels from moving when the tank is inverted. If the reels move, the top and bottom edges of the film tend to get over-developed because of the way the developer repeatedly flows through the reels. The idea of the airspace is to allow a more random pattern of developer flow
"...while plastic reels and tanks and may somehow, someway produce sharper negs..."
Not sharper, more even. George hypothesized that it was due to the larger spiral made by the film in the plastic reels. Anyway he got the very best results in Paterson tanks.
I use stainless tanks and reels, too, even so
