The main thing I have against alternate engines is the they are so many experiments all rolled into one aircraft. every part that has to be adapted to the application is an experiment in itself. when they say they had to modify the crank, add a thrust bearing, put on a different carb, added a balancer these are all experiments that may or may not work as planed. even if they do work, for how long? when they claim that it has flown 200 hours without a problem, it is still an experiment and what will happen on hour 201? as for the mass of the engine that Burt designed the varieze to have, that has been an experiment that went the other way. so successful is the design that people that have experimented with bigger engines have proven the design to be able to handle the load safely. if you are looking for dependability with the least maintenance( best proven TBO ) go Lycoming second choice is continental