Comment by agalunar

You’d perhaps be better off using U+2002 EN SPACE (or the canonically equivalent U+2000 EN QUAD).

From what I recall, the size of a typical interword space is ⅓ of an em, and traditionally a bit more than this is inserted between sentences (but less than ⅔ of an em). The period itself introduces a fair amount of negative space, and only a skosh more is needed if any.