Traditional customizers are creative people. While they might be introverts, they want to sign their work. You can tell a Barris or Starbird or Jeffries custom across the show floor.
But a Rivvi - already customized on its first day - requires different solutions than the usual torch work and mishmash of elements. The build does a great job of beind selective with the Villa Riviera parts, choosing a less gaudy path.
For inspriation, IMHO Bill Mitchell's own Rivvi, "Silver Arrow 1" is instructive. He chopped the roof and stretched the front fenders to slightly past what he wanted in the clay model. (Tim Boyd's build on the magazine cover approximates this chop.)
After slamming it about 2" it on Skylarks and 3/4" whites and a little messing with the ornamentation, Silver Arrow #1 was done. Fini..
But even someone who got it right the first time can whiff - the 1977 Silver Arrow 1 "update" shows the worst of Mitchell's "Great Gatsby" tendencies, as he re-signed his magnum opus. (Historians suggest that GM gave him the checkbook to work on pet projects to distract him for the big downsizing projects, which he fought to his last day in the office. ) The updates including Rolls 'beehive' wheel covers, wide whites and the single panel grille take away much of the energy that made the original Silver Arrow great.
Now retired, GM Design Ed Welburn SVP did not order SA1 to be returned to its original state (the first wheels are rumored to hide behind the current covers,) such is his reverence for Mitchell, but more's the pity.
The first version is always the best.