I believe the FRA are awaiting a candidate to trial them in heavyweights. Id say big nipper would be the perfect candidate. Due to the team already having lipo experiance and the fact the robot is well enclosed should anything happen.

When i proposed heavyweight use of lipos the FRA's outcome at the meeting was they wanted to see some destructive tests for themselfs.. I dont think its neccasairy due to the amount of videos on youtube about it.

If pierced.. they smoke alot
If over discharged they do go pop.. but you should have a fuse inline anyhow to prevent this.
if over charged they can go pop.. But you should charge them in a lipo sack anyhow so it shouldnt be an issue... again just more smoke will come out the bag... And the fumes are only as bad if not as bad as nicad fumes.

I carnt see them getting pierced in big nipper.

What pack configuration are you thinking of using and how many amp-hours? Aslong as its not above 10c 20amp i think the FRA came to the conclusion it should be allowed..(I think it was 20amp.. carnt remember)

I think its down to the EO's more then anything.. Contact Jonno or Alan to see what they think about you using them in there arena's.