Stringer Glue-Up?

I’m no pro builder, but for my 3 lb EPS I don’t feel spackle is necessary.  Plenty much dense and less resin penetration/absorption.


Another semi-related question.  For another project, I want to bond the hotwire cut surfaces of 2 pieces of 3-lb EPS foam together.  Would you folks rough up the cut foam surfaces a little with sandpaper to improve epoxy adhesion?

Missed this one.  Thanks.

If bonding two (2) hotwire cut EPS foam (3-lb) surfaces, do you prep the surface with coarse sand paper?