Having done plenty of them using the donor No42/53 ocular end and got it off to a fine art, I'd just say that going down the 'making from new' road is over complicating matters. I have had to re-repair two previously repaied by the by the silver soldering method when the butt-joint between the taper and the large ocular diameter had failed. Anyone going down the new ocular end road should consider a threaded or sleeved/undercut joint of say 5mm or so long/deep the join of which is mid way under the rear cradle cap. There's loads of strength in the join which is reinforced by the clamped cradle cap.
And thanks for all the thanks chaps. Nice to assess the feedback