The shoulder pad also defines how much you can change the length of the whole strap - the adjuster can't tighten beyond the beginning of the pad of a shaped strap.
If the strap is the same width all along its length - just a belt with holes at the ends - then an adjuster can be used to almost halve, (or double), the length. An elegant tapered design can't do that. Ah. Form versus function again...
Many of the mass-produced leather straps - and some of the 'custom' ones that I see for sale - use one of two solutions.
For a belt-like design, a simple three-bar slider of the sort used on straps commonly sold for acoustic guitars will work. Quite effective on a leather strap if you want that no-frills style. The slider can end up on your shoulder, though.
The other popular option uses a ‘slot-ladder’ arrangement in the pad that the main strap weaves in an out of. I'm not very fond of that, visually, plus the strap has to fold over itself in a spot where I don’t want my straps to be bulky.
NEXT: Adjustment Range