I started with a 2008 S-40 with 1200 miles on. I always liked the old British singles from the 50s-60s so I thought I'd build one.
The tear down and first mods. where like a Ryca build,18" rear wheel, modified swing-arm,etc.
Then I added a loop on the back of the frame.

Under seat area. You can see the Progressive shocks that are an inch over stock.

Fabricated kick-stand bracket with the stock kick-stand. Shift linkage rotated around to a Ryca style mid-mount bracket.

Stock brake pedal moved back. Stock brake light switch moved to a tab on the bracket. Sportster foot-pegs. Emgo muffler.

Royal Enfield seat, Sportster bars extended 2" on each side, Lucas style tail-light, home-made rack, fenders pounded out of 18 gauge mild steel.

Home-made front fender, rubber fork covers. Forks are stock length.

Right side. Home-made exhaust. I was going to go with a high pipe on the other side but went with the Gold Star look. Pipe is 1 1/2".

Left side is simple looking.

Relation between seat, bars, and pegs. I'm 6' 195lbs.

Other side.
I took it for a chilly ride (47*f) and I'm really happy with the way it turned out.
Carl