On Thursday, May 28, 2020 at 7:29:56 PM UTC-6, wrote:
"I need to come up with a method of preventing the first wing from being pushed out by the second wing..."

On SH left wing goes in first, pin goes half way in, then I stick a piece of wood between the end of the pin handle and cockpit.

That's the way the Phoebus rigs as well. Left wing in first, pin goes in through one fork of the spar, insert right wing, push pin all the way through both spars.