I really like what Chris has done and have reached out to him. What's on my mind is two 40kg class engines. You would have 175lbs of thrust, and in the event of one failing, you still have an adequate sustainer. I'm estimating the system would be around $25,000 (15k for the engines and 10k for the install). Where I am guessing entirely is the cost of the install, and if there would be enough room for two of this size engine. Two P300s are 10.5" wide next to each other, while two 40kg motors would be 11.5". So it seems they would fit in a lot of cases.

Interestingly, the P300 has a bit of a track record of catastrophic failure.. I'm sure there is an explanation out there as to why, but I followed many incident threads and I never found a definitive answer. There was speculation that the rotor sizing resulted in a resonant frequency that was causing stress on the bearings.