I just started Joes' Spring Run about 3 weeks ago. The offset you mention was right at 1/2" so four 1/8" thick strips did the trick.
If the offset had been 5/8" I would have added 1/32" to each of the 4 strips or gone to five 1/8" strips. Not sure why it's impossible to get a glue up to match the offset. Are you ripping the strips on a table saw?
Yes it does matter so far as getting maximum glueing surface when shaping the stem, especially the last few strips that intersect the stem.
As Joe suggests, it's best to shape the stem in sections as you add strips because the optimum flat surface changes as you work up the stem.
Patsy I hope this helps. This is my first post and first build so clearer answers are sure to come along.

Ian

Joe's instructions say that the offset between the top of the last
: station and the attachment point of the bow and stern forms
: equals the thickness of the inner stem. Since it is impossible
: to get a glue up of the inside stems to match that exact
: thickness, the forms are going to have to be a little bit above
: or below the line on that last station. My question is does that
: matter? And if not, why not? I would think that having the bow
: form above or below where it was designed to be placed would
: change the bow of the boat. Is that not true or again, does it
: not matter?

: Thanks,

: Patsy