the 44t sucked, and I think it contributed to burning up my first motor. I wish these came with 36's. Plus, I got such a smoother running chain and easier starting with the smaller sprocket, oh hooray. I bet that is how a lot of people dislodge their rag joints; pedal starting the engine and not going fast enough before they dump the clutch, combined with flexy standard 14 or 15 gauge spokes.
Here's how I did my cog: I just filed out and press fit the cog on the hub without the dust cap, and ran the rubber donut and 3 metal plates in the center. (some might need to use some JB weld or something if their center-hole is bigger than their hub , or just back the cog against the spokes only like on some freewheel hubs.)
http://www.facebook.com/video/video.php?v=1498268634583&saved
re: 38 hole wheel.
I've never seen a 38 spoke wheel before. That is just weird. I've seen 100 spoke wheels and 72 spoke wheels, 16, 20, 28, 32, 36, 40, and 48. I guess since it's straight laced, it doesn't matter as long as it's a multiple of 2. Have you had any trouble with broken spokes?
re: metal rag joint adapter. It looks like a heck of a deal to me, since it would be easy to re-use on a different cog or wheel later. If I was going to build mb's for sale or family members, I'd never give them a rubber rag joint bike.
People won't really bother changing sprocket sizes on a bike. they just won't. It's not like "hey what a great day today - I think I'll change down up from 36T to 44T" because there is a lot more involved than just changing the sprocket. For every size of sprocket the chain length is different and working with a filthy chain isn't my idea of fun. Then there is the setting up of the chain tensioner. I had two identical rear wheels for my 4-stroke. A 48T for everyday and a 44T for fast motorway runs. Guess what? After one attempt I decided to stay with one sprocket size and that is what any sane person does. It's not just the sprocket its the chain and tensioner.