There is no such thing as how it "should be done", for me that's the joy of these silly things, there is no "right answer", just variations, and for me that's a great thing.
Each of the ones I have part done so far explore different ideas and methods within a very meagre budget. Original Stevenson for the ERA except using 60 x 30 x 0.7 mm rails, pure plywood for the Austin, separate chassis for the Bentley, stressed skin alloy with a space frame for the Voisin and all of those were runners. Then there was the GN Kim, wooden chassis rails, plywood monocoque with thin alloy sheet jut like the old MG Midge. I think that qualifies me to say I don't slavishly follow a " method". Did they work, yes all did, which was better or worse? The Bentley was at the bottom of the list with a separate chassis and body on top. They have all been fun, and all a thinking exercise with new skills to discover. Next is reverting to what Mike Stevenson suggested in the first pace. Will it be completed? NHS will have a big say in that.
Bodily medical stuff may throw some hiccups in the way, a cancelled operation due two covid hasn't been a great friend, and another waiting list .