Thanks for the info Dave, the Riser came with a 1/4" OD steel rod and a 1/4" ID brass outer sleeve like what you use. I have a Sig Kadet Senior that has the flat aluminum type like you were talking about, the steel rod seems better to me by the way you described it. I made balsa ends for each side of the brass sleeves, glued them in place and then propped up each end of the wings and glued it in place to the spars using CA.
Tomorrow I plan on installing wood wedges between the sleeve and spars, add the sheer webs than stand them up and fill the rest of the cavity with epoxy like you suggested. It seems the Riser is going together quickly and I'm thinking of mods while at work today. (couldn't help it
1. Electric motor
2. No counter balanced rudder
3. Slip in front wing hold down instead of a bolt.
4. Magnetic hold down on the hatch
5. Use Sullivan Gold-n-Rods for rudder/elevator
6. Servos for the Spoilers instead of string.