There is a sentiment that non-certified vehicles cannot be as safe as certified ones, but certification does not and cannot substitute good engineering and thorough testing.
Certification is arguably the most expensive stage of a new aircraft development and is seen as the validation of the safety of the design. But certification is not a substitute for sound engineering and thorough testing. A lot of industry experts feel uneasy about FAR103 designs because they have not demonstrated compliance with certification standards. The key word here is ‘demonstrated’. A design that is based on the experience and best practices can be just as safe as one that has been through the certification process, just as a certificated design can have problems that were not uncovered during the extensive compliance demonstration. According to a BBC article, ‘the Boeing 737 Max has been described as "the most scrutinised transport aircraft in history" after a series of safety issues’ and, the article continues, ‘Aviation expert John Strickland said the Alaska Airlines incident was very different to those crashes, adding that since the 737 Max came back into service it had "an enormous safety record".’ Enormous safety record or not when a system is as complex as a modern day commercial aircraft it is imperative to resist the pressure to deliver before the design has been verified it will be safe. When I designed and built my first aircraft, the Stinger (an all metal wing FAR103 design) which evolved into the Solo, we took over a year to test and verify the assumptions and solutions before we offered it to the public. And it was an extremely simple design. When I took off for the first test flight I had no trouble flying it without a parachute as we had tested even the behavior with components not installed to verify the failure modes since it was offered also in a kit option and we knew to err is human.