The standard stop-loss level for an Ideal Butterfly harmonic pattern is the 1.414 extension of the XA leg. In this case, 2004.51. This would be very close to my stop in a Forex or securities market.
However, due to the inherent volatility of cryptocurrency markets and their widely varying prices across exchanges I use a wider stop when trading bitcoin (or any other crypto). Personally, I create a basket of various BTCUSD markets to get a feel for the current price-range and go from there. More art than science, I'm afraid. :-)