Ah, now, this is where I start to become confused.
My Indian Lightning stem is too short at 25.5cm from the top of the ball race (it needs to be about 26.5cm), but yours, which I assume did have the top nut screwed down onto it, is only 24cm!
Good job we're talking Royal Enfields, as this doesn't have to make any sense...
I measured a couple more bottom yokes, a standard Bullet (pre-2003 Indian?), 23.5cm stem, and a Series 1 Interceptor, the shortest of the lot at 22.7cm, both also measured from the top of the ball race. Both of these use sleeve-type top/stem nuts.
The Interceptor item is new old stock, it has the plate with 2 pegs welded onto the bottom for the steering damper and has a hollow stem to suit. Let me know if you need it for your project.
Thanks for checking!
A.