You don't pick a speed rating and THEN decide to develop it at N or N+1 or whatever; that's backwards. You pick your N/N+1/etc based on the SBR and that determines the development time, which in turn defines the film speed that will be achieved and therefore your meter settings.

If you're developing at N+1, the rating of the film is likely to be higher than box speed, not half thereof even though you're using Rodinal.

You can of course decide to develop at N+1 if you don't have enough light and need the speed... but you do need to be aware of the high contrast.