i would advise to avoid sealing, as monokote under sun liberates gas from the adhesion material endless. if sealed the air canīt go anywhere and may develop riddges hard to iron back and even delaminate on the sealed areas.
One of my best glider flights was about 30 years ago with a Goldberg Electra. I launched it on a hot day, and after getting a couple hundred feet up it just took off. It was just a speck up in the sky, and I had to give it a turn command and wait 20 to 30 seconds to see which way it turned so I knew its orientation. I was up for about an hour and a half when I had to bring it down. When it got on the ground, the covering was all puffed up. I had only sealed the edges of the wing and the heat and outgassing filled the wing with no way of escape. I guess the new airfoil section it got from being puffed up made it super efficient or something, as I wasn't thermal hopping or anything. I don't know how high it actually was, but the reason I had to bring it down was that we shared the field with ultralight planes and skydivers. Obviously, when one or the other group was up we stayed grounded. But on this day the skydivers took off from the B'ham International Airport, about 15 miles away, so we had no clue they were coming. The first warning we had was when a plane way up high cut its engine back and the little dots falling from the plane. As soon as we saw that, I gave full up and full right to spin down as fast as I could.
After we packed up for the day so the jumpers could have the field I went to the local convenience store to get a Coke. A couple of the skydivers were there getting goodies and one asked if I was one of the model plane guys. When I said I was he asked if I know who owned the blue and white plane. My glider was blue and cream, but I just said, "Yeah, I think I know him". The jumper told me to tell the owner that he passed the plane at 2,500 feet on his way down...
Not control line related, but an interesting anecdote that I just remembered. After that flight I sealed the covering down good and made a hole for the air to escape. Never had that good a flight again.
Mark