I have built 4 Northstars, so have developed my own mods for it that I believe are appropriate and make it an even better flyer than Laddie originally designed. Laddie seemed to agree with that assessment the last time he looked them over.

For the elevator I have a balsa piece glued to the bottom of the nacelle behind the tank through which I run the Nyrod. You can easily make this in two pieces and CyA them together and to the nacelle if you want, but in either case you will need to change the trim as you will likely be changing the effective length of the control rod. Here's a picture of one of mine in which you may be able to see the mod - behind the balsa end piece that is removable. Hope that this helps...