For Serge, The covering is silkspan applied with 50/50 Elmer's white glue and water. It then gets one coat of hot water/unflavored gelatin mix, one packet to 1 1/2 ounce hot water. This provides a seal where you can pour lacquer thinner on the foam! I've been doing this since '73. You mentioned the wing gap. The RM wings have a 9" average chord. Measured here at high point to high point the separation is 5.5".
For Gordon, click on the photos to enlarge. All the specs are in captions.
I hope to fly it next weekend.