"I use an int because the pinMode and digitalWrite functions take ints."
" Using ints means that things wind up on even byte boundaries, which might be a good thing "
In the datasheet 8.3 SRAM Data Memory shows the SRAM Memory as 2048 x 8 in Figure 8-3. Data Memory Map, which would seem to be in disagreement with the latter statement.
And this also says to me that ints are not required to use SRAM bytes directly:
"The direct addressing reaches the entire data space.
The Indirect with Displacement mode reaches 63 address locations from the base address given by the Y- or Zregister.
When using register indirect addressing modes with automatic pre-decrement and post-increment, the address
registers X, Y, and Z are decremented or incremented."