Brian,

You could take one of the boats like the See Bee and make it narrow by multiplying the horizontal measurements by the ratio of the beam you want. See Bee is 24", to get 22" you can just multiply by 22/24 to get a nice even shape for a smaller weight. I did the same to the Sea Tour 17 EXP.
Any particular reason why you don't want the multi chine version of the See Bee? I just finished building one and it really is not much more work. 4 extra stringers exactly the same size, a little more cutting on the bulkheads. No real problem.
Trying to change the spacing introduces a problem. The cockpit area gets proportionally smaller. Not a problem for your son, but for me it made the cockpit just too small. I am a little bit FULL sized.
Have fun.

: I am getting ready to build a skin-on-frame kayak for my 12 year
: old son. I liked the 13 foot Sea Bee single chine on the
: YostWerks website but he says the offsets for it are not
: available. I liked the look of the Sea Cruiser but since my son
: is only 110 lbs that is more boat than he needs. There were
: offsets for a 15 foot version of the Sea Tour but I think we
: favor the profile of the Cruiser to the Tour. I am considering
: using the Sea Tour 15 section spacing with the Sea Cruiser
: offsets. Am I nuts? More importantly, can I do it?

: Are there other sites where I can find free skin-on-frame designs
: or does anyone know where I can find the Sea Bea single chine
: offsets?

: My son was suppose to take a sailing camp this summer but I
: suggested a kayak instead so I only have about $250 to get him
: outfitted (kayak, paddle, PFD, etc.).