If you think 1/2" really would make a difference, I would sit in a few brands.
Reason is; not every brand will feel the same, the Tree is measured before leather, padding, etc. is applied.
Saddle Makers use various thicknesses of padding and leather, plus if it is a wood tree, the tree itself will vary 1/4".
Personally a 1/2" in seat size is no big deal to me, depends on if you are trying a Saddle out before or after a Thanksgiving dinner