Newel post to stringer on first step

[Roys]

Renovating my full house, doing the hall just know.

The house was built in 1962, it had a Parana Pine staircase which had a ranch style banister with 45x90mm posts half lap jointed onto stringer with just a plank top and middle, you know what I mean.

So stairs sanded back with old spilt paint and old horrible dark yellow varnish sanded away back to the bear wood and a satin floor varnish applied, I think it looks good even if I say so myself.

Next stage in the plan is to create a newel post top and bottom with a stainless steel bannister with glass, screwing the glass clamps straight onto the stringer.

What I have done is join two of the 45x90 posts together by biscuit jointing and glueing then put it through the planer thicknesses to tidy it up. This has created 2 off 87x87mm posts.

My question is the attachment of these posts, the top post I chopped out a slot and fitted it over the stringer, is it just a case of putting 4 off 5x80mm stainless screws through it to secure.

The bottom post I need to fit onto the first tread, so do I just repeat the same process as the top post and screw through both legs of the post and stringer?

Stringer is 45mm. I need to attach to first tread to bring bannister length down to below 4000mm which is as long as I can get the bannister.

cheers gents for looking.

[Roys]

Nobody know the  best way to fasten newel post to first tread?