I'm uncertain as to exactly what you mean by "battering". But I think there are a couple of things to take into account. Firstly, one can process using a Paterson tank that does not contain its full capacity of reels. But this doesn't necessarily mean the tank won't be filled to its maximum capacity of developer. (Indeed, depending on the type of developer used and dilution it may potentially be advisable to fill it completely, to guard against exhaustion in some cases.). To put it another way—a tank might be half full of reels, and full of developer—or, it might be half full of both. What applied to your roll in question?
Secondly, I've been routinely buying and using used Paterson tanks and reels for years so must have 25–30 reels and a dozen or so tanks, (both System 4 & Super System 4) in sizes from a small single 135 to my largest which can accomodate up to 8 x 135 (or 5 x 120/220). There's considerable variation in the fit between reels and centre light trap column. Some are so loose reels literally slide with gravity. Others hold reels more tightly in situ. Not sure why there's some difference—I presume age and/or use. But, if a tank will not be filled to full capacity, it is, in my experience, not prudent to assume reels will remain locked at a low enough point on the column, by themselves, to preclude tide marks or other artefacts. They may well. But might not. It's a risk entirely avoidable and hence, not worth taking.
Indeed, Paterson originally supplied C clips made of the same material as their reels with their tanks, the purpose of which was to lock reels in place and prevent uneven development. Their instructions specifically advised not to store the clip on the light trap when not in use. If you do, eventually they stretch, and become ineffective. This is a problem for anyone who sources used Paterson tanks and reels: the clip will usually be absent in the first place. If it's not, you may be assured it'll be...sitting on the light trap, well stretched, and...no longer effective. I have three or four clips. None worked terribly well, when I acquired them.
One work around (if you won't be completely filling a tank) is to fit an empty reel(s) above the loaded one(s). This will keep loaded reels safely immersed (assuming, of course, you have added the correct quantity of fluid per reel). I have done this many times without issue. Another simple hack is to take a standard Kodak 35mm film cassette container and cut the bottom out of it with a sharp knife. You then have a basically free spacer which may be inserted into the light trap above your reel( s) to prevent same from sliding above the high fluid mark during inversions.
Being fortunate to have a variety of different size tanks I can usually match the numbers of reels and times/dev type/dev dilution to tank capacity well. Occasionally however I may use a tank only partially occupied with reels. Case in point, just a few weeks ago I had my 8 x 135 3/4 loaded with a combination of 135 & 120 rolls that take the same dev and time, but which would not all fit in my 5 x 135 tank. I had no problems with any of the rolls involved, although, in that instance, the tank was completely filled with developer. On the rare occasions I process with a tank only partially filled with developer, I will be a little slower and gentler with my inversions than when a tank is full, simply because developer can slosh around more "violently", inside a partially filled tank.
The 8 x 135 Super System 4 tank is an interesting case study. It was a freebie (needed a light trap of the correct length which I fabricated from parts) however I was wary of possible development problems because of its size. And due to its sheer length, it takes longer to invert than smaller tanks. When filled just above the top of the light trap (not the lid) you can feel the dev take a good second to surge from end to end and displace the residual air inside, when you invert it. @ 10 seconds inversions per minute I only invert and return the tank 3 times or so. Despite initial concerns, I've had good results out of it, but I do make a point of being consistent with inversion technique with any tank, but particularly that one (and this is perhaps the overriding consideration, regardless of tank size, for good, predictable and even development).
