I believe for a model as simple as the SE5a there is plenty in the Easy Built kit. The Guillows kit is so over built for a boxy fuse. Simplicity is the beauty in a plan like that in the Easy built kit. At 18" the wing rib spacing should be as little as possible. Again just like the 400 series kits the Guillows kits are not built for rubber power duration. As far as the wing chord being different I would check against a 3 view that did not come from either kit to see which might be correct because they can't be the same WS and have a different chord.
Your model looks great by the way. I wish you a ton of success with it at West FAC!
Steve