I wince whenever I read the terms 'magic gear' / 'not using a tensioner' in a thread.
Respect to anyone who is doing so, but I think it's daft. The only way to get correct tension ALL THE TIME with vertical d/outs is with a strong sprung tensioner.
Rings are often not 100% perfectly round for starters, and magic gears only 'work' in a small range of ratios. Plus aren't you straining the drivetrain?
And don't get me started on that mech hanger just dangling there with nothing in it!
I do however like that chainline checking method, from the Mtbr forum
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vintage Brooks Professional saddle | Specialized FACT CX fork | Columbus fork | Reynolds 531 fork | Avid Arch Rival v-brakes | various 700c, 27" and 26" wheels | vintage Weco hubs (fixed/freewheel) | vintage Raleigh ladies frames + lots more!