Spiralling should be heavily discouraged everywhere with more than 2 canopies in the air, except if you are the lowest one and with a fall rate in full flight comparable to the ones above you. It develops 0 skills, it is an unsafe practice for the one doing it (can collide with other canopies that he/she didn't see) and for others (don't know where to go because the one spiralling is not flying predictably) and it gets boring rather quickly, so it is not even fun compared with other things you can do under canopy if you have the skills for it.
To minimize conflict under canopy, you want to maximize both horizontal and vertical separation, and "pipeline" the canopies landing. A typical situation in medium size dropzones is having 18 canopies in the air at the same time. If you are in the middle of the bunch and have a canopy loaded at, let's say, 1.5, the safer way for everyone is if the heavily loaded canopies after you overtake you up high, and the vertical separation between these 2 groups is not reduced after that. That way there are no conflicts close to the landing pattern. If you start spiralling they can't overtake you at a safe altitude, since you artificially accelerated your fall rate, just to stop to your normal rate as soon as you stop spiralling. If you start-stop and then start and stop again, that makes it even worse. Like a car in the highway driving on the left lane and slamming on the brakes just to swerve to the right, accelerate, move again to the left lane and slam the brakes again. So the ones behind with highly loaded canopies need to do either of these:
- Overtake you in the pattern. Take into account that the *last* turn for many canopies starts at 1000 feet. So your pattern starts when theirs finishes. Nobody wants to overtake or be overtaken at this point, every one should be focused on the ground and landing safely, not on canopy slalom.
- Land out. Not always an option, depends on the DZ.
- Hold on to breaks as much as possible, forcing everyone behind to do the same. This is not always possible, as even in brakes some canopies that are heavily loaded fall faster than other lightly loaded canopies in full flight.
All these options are bad. This situation is quite common, as belly flyers typically fly lightly-to-medium loaded canopies and exit first due to free fall drift, and freeflyers have a higher tendency to fly medium-to-highly loaded canopies and exit after the belly groups. The exit order helps to keep horizontal separation between groups, but minimizes vertical separation as both groups open at a similar time and altitude. To fix that heavily loaded canopies should land first for everyone's sake, but can't do that if the lightly and medium loaded canopies are spiralling. Some would blame the small canopy and say they have the right to spiral down. Others would blame the spiralling pilot for lack of canopy etiquette and being equally skill-less and a dick.