Very easy to make a "tool" to prevent the left wing from coming out while inserting the right wing. Just a block of wood cut the correct length and cut with a hole saw on one end to match the spar pin and rounded on the other to match the fuselage. Put the left wing in, insert the spar pin part way so that it does not extend beyond the left spar. Then put the tool in between the pin and the left side of the fuselage. Not needed if the plane is cleaned and lubed properly but can be helpful on very hot days.