All I know is when balsa is used it is end grain blocks. It seems you would be asking for problems down the road with a soft core. Why don't you do a test panel and post the test for us:)
Don
: There has been a fair bit on the forum about the strengths of different cloth
: layups, but what about the wooden core? Since the strength of a hull comes
: from fact its a composite would a wood that is harder then Cedar make the
: composite so much more stronger? Likewise what about a softer wood?

: The reason I'm asking is that I'm down to the last 5 strips (on each side) of
: the hull football area on the Night Heron and would like to use Paulownia
: instead of WRC in this area. Paulownia is can be compared to a stronger
: version of Balsa. It dents easily but is flexable and close to the
: strength of WRC when you break it - measured by the very scientific method
: of snapping strips

: I plan to use 2 to 3 layers of 3.25oz cloth in this area. And yes I will be
: rock gardening and landing on bouldery beaches but my 6oz clothed ply
: kayak has survived 2yrs of this abuse with out any major scarring so I
: think I can get away with a lighter hull.

: Thanks for your help.
: GrantG