| Just gone throught the same exercise myself. As you probably have, I've done quite of bit web searching and asking around. Know was mentioned lots as in the above posts. However, in the end, I opted for the Forcefield T-Pro, not least because some racers I spoke to have recently switched from Knox to this one, and when I checked with Hideout leathers, who sell both, they also recommended the T-Pro. The make a race version which protects your tail-bone (as do Knox). It is more pliable and fit easier under leathers (at least in my case). I was pretty impressed and have also used Knox in the past.
IMO, either one will do the job. Best advice, try them both. | 
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