According to the "tribute" web page and the FAA registration database, it was a Columbia 400, not a Lancair IV - not a homebuilt, a certificated aircraft. He didn't build it.
As far as six folks goes, two of them were very small children. It's certainly possible that he was still within W&B limits, although the seatbelt situation can't possibly have been legal.
The description of the accident sounds like a stall/spin on climbout after a go-round. The valley near the Kern Valley Airport is extremely narrow, with hills on either side that are hundreds of feet above the airport, with very little room to turn around. Pull up, turn too tight... Done.
Landing there was interesting, in gusty winds, to say the least.