The loc viper IV is 17 oz so 17oz X 4.48 (to convert newtons to Lb) X 6(very conservitive minimum thrust to weight) / 16( to account that I use oz insted of lb) so that leaves me with an average thrust of 28.56 N so basicly you could fly this on any 2 motor that has An average thrust of 15.25 N, hopE this helps
NOTE: do not use 2X D12 a it would only provide 24N, assuming it had an average thrust of 12N, but it doesn't it only has a certified average thrust of 10.21 N