I'm replacing some windows in my house. The original window openings were outsized for the rooms, so the replacement windows I've chosen are smaller, which means framing in the part of the opening that I won't be using.
The first window that I'll be replacing was off-center in the wall, so I'll be installing the new window to one side of the opening so that it will be closer to the wall's center. As I see it, I need to create two pieces of framing -- one for the side of the window and one for underneath (I think a single L-shaped piece would be structurally weaker). There are two ways that I could build these pieces: one where the side piece fills the opening vertically with the bottom piece at its side (Figure 1); the other where the bottom piece fills the opening horizontally with the side piece and window resting on top (Figure 2).
Figure 1: Side framing piece fills opening
Figure 2: Bottom framing piece fills opening
Have I considered all the options for how to build the new framing, and is there an advantage for one method over the other?