owners of aircraft recently moved to Permit had uncovered years of poor maintenance done by approved engineers and only discovered by LAA inspectors
That's not really a relevant comparison though because any owner with some engineering mentality can make sure a CofA plane is maintained properly - whether he can do the work himself or not.
All this means is that there is a strong correlation between engineering/DIY-savvy people and homebuilders - hardly suprising!! All those who cannot / do not want to pick up a screwdriver but who still who want to own a plane go and buy a CofA one and hand it over to a company for every service, with a signed blank cheque left on the seat.... and then they wonder they often get a crap job done. The maintenance business is a Russian roulette and always will be.
Against that I see a high proportion of homebuilt accidents involving structural failure which is extremely rare on the CofA scene. One needs only to walk around any homebuilt show to see how flimsy a lot of them are. To get the weight down, something has to give somewhere...