I have to scale up the cell size from the 4x6 to 11x17 to fill the frame, so the scaling is appropriate.
This is suspicious. I think my original suggestion is apt.
2) I can't see how I'd make a new template without it being based on the currently selected template - i.e. 4x6. I do save out a template to save my color management/printer/paper settings (the main reason I prefer printing LR rather than PS).
1 Start with your original 4x6 template that will bring in appropriate media and colour management settings.
2 Now go to Page Setup, and choose your new paper size, then
3 go to the main (top of window) Print menu and select 'new template'. Give it a name and save.