In all my years of shooting and careful observation and testing, a free-floating barrel is only as good as its rigidity and how well it is anchored to the receiver so that during the shot cycle or even a slight bump will not change its point of impact. On a (air)tube-type PCP, a free-floating barrel is pointless if the barrel is flimsy. It's why the Air Arms S4XX series utilizes a barrel clamp to make the barrel stiffer and unaffected by vibration, bumps, harmonics, etc. I have tested my S410 to see if the barrel moves by mounting a laser to the shroud and superimposing its dot to my zero distance at 27 yards. No matter what I did to the barrel, which was push it side to side and up and down and even shot the gun from a full charge to no charge at all, it held on to zero. You can see for yourself by doing what I did if you have a S410 or similarly designed gun, the barrel will always return to its original position provided it's held securely to the receiver.
Personally, I like the design of that of the Cricket or bullpups that use its barrel-to-scope-rail mounting system. Basically, the scope (which is mounted close to the midpoint of the barrel), by means of the rail/clamp, enables it to point wherever the barrel is pointing. With either design -- free-floating or not -- accuracy on my TX200, S410, and Cricket bullpup is no different than each other. They all are precision shooting weapons when I'm up to the task.