In Denver’s plane, the builder relocated the fuel selector, deviating from the plans, and that caused or contributed to the crash. Even in a match-drilled Van’s RV “assembly” (rather than “fabrication”), a builder might very well decide to do something like that, and has the freedom to do it if he can sell it to the DAR. As the builder of Denver’s LongEZ did.
The builder also made other modifications, such as installing an engine that wasn't approved by RAF. It led to CG issues that were solved by installing forty pounds worth of batteries in the nose.
Home builders deviate from the plans all the time, kit or fabrication.
That's one of the great things about homebuilts...whether you construct from plans, a kit, or buy an already-flying airplane, you can deviate from the designer's intent however you wish.
But I believe it's less common in kits than in plans-built aircraft.
Why does someone build a plane from plans? It might be that the plane caught their eye, it might be that the performance or other features match what they think they need. When they start building, they know they'll have to exchange thousands of hours of their free time to possess the plane. And I honor them for it.
Kits? Well, they get selected the same way. But when they start building, I think the majority of the builders JUST WANT THE DAMN PLANE. Companies wouldn't SELL quick-build kits if people weren't buying them. They wouldn't hold "Two Weeks to Taxi" programs if there weren't people in a hurry to get their new kit flying. And I honor them, as well.
But everybody understands that if you decided to modify the design of a kit aircraft, it's going to add to your build time. If it's something the builder feels strongly about, they'll just go ahead. But most builders just want the damn plane.
We don't know how many "Quick Build" kits are sold vs. "regular" build. But there's a hint in the registrations for Carbon Cubs. "Normal" kit versions of the Carbon Cub have a model number with "CCK", airplanes sold as part of their builder assist program are "CCX". You can check the FAA registry to determine the population size for each.
From my January 2020 FAA database, there are 113 CCK models (traditional kits) vs. 116 CCX (Builder assist) models. And note that the builder assist program came in later; the oldest CCK model in the registry is a 2009 model, vs. 2015 for the first CCX one. Equal fleet size in half the time.
Now...if someone buys a complete kit, they're not likely to want to, for instance, throw out the whole fuel system and install their own design. This is probably even truer with a quick-build kit, and I'd bet the "Two Weeks to Taxi" programs don't allow much variation as well.
So I think modern kits are more likely to be subjected to fewer significant builder-initiated design changes than plans-built aircraft are.
The Vans airplanes are probably the exemplar of modern homebuilt aircraft kits, and their safety record is very good. It ALSO improves when you get to the later model airplanes, which had more-complete kits and the availability of quick-build kits.
Ron Wanttaja