Melting a hole in a piston is easy. All you need is for the mixture to be too lean and Nitrous effectively adds oxygen so leans out the mix massively unless you add a lot of extra fuel. Gas burns SUPER hot very close to the spark plug if leaned out too much, and that hotspot eats into the piston crown until it burns through and you lose compression.
I had N2O on a Yamaha XS250 back in my late teens and we holed a couple of pistons before we got the mixture right. Was fun though as we had the only 250 that could stay with 750s off the line and could get to 115Mph.