I had converted the steering head bearings to tapered rollers, easy job and have a good axial load capacity.
This is a pic of the set up in a TL1000.
Koyo caged inner ball bearing (I could not find a suitable Koyo race to fit the Norton) with cups of sorts.
It is little different to many Japanese bikes or bikes that came with tapered roller bearings stock.
The bearing clearance is set by the adjuster locking ring on the stem, the other locking ring locking to it to hold that setting.
The (upper) triple clamp sits on top of those locking rings and its top ring locks the triple to the two lower locking rings with no ill effect on the bearing clearance.
Seems simple enough.
What happens if you want to add taper roller bearings to a later model Commando.
The first problem is the design does not allow bearing adjustment while retaining the mechanical integrity up through the stem from the tight bottom nut.
Ball bearing / inner spacer tube / ball bearing / lower triple / large nut tightened 'really tight.
Seems simple enough.
The internets seem to suggest you just leave the inner spacer tube out with tapered rollers which means the large lower nut with its coarse thread becomes some form of bogan adjuster and left all but finger tight.
The tapered roller bearings I found left the inner spacer tube to short.
All I did was face both ends of the stock spacer tube then machine a 4140 heavy shim lapping the last 0.001" to size to set the bearing clearance.
The alloy tube replaces the lower triple clamp for ease of initial setting of the bearings, the lower nut is cranked tight.
It has Morey's Bigfoot EP 2 grease for its tackiness.
I used Moto Guzzi final drive shims before discarding those and machining a heavy shim.
What does it mean.
The bearings are adjusted and stable, the lower nut can be tightened as it was meant to be.
You will still get people saying the inner tube can be left out, good luck adjusting the bearings if you do.
The taper roller bearings cost pennies more than the ball version they replaced.
To easy and with that grease will never need touching again in my lifetime.