Those are great clamps Erik, I bought mine as a 3-pack. A little pricey but well worth it. There was mud. I prefer to use a method the requires no sanding to save surrounding details.
For those unfamiliar with this method, here's how we get there. You'll need nail polish remover, Q-Tips and mud. There's a whacking great gap at the rear of the wing/fuselage join. I was going to fill it with plastic strip and sand but this kit has raised panel lines. I have replaced these with stretched sprue before but it is a right pain in the keester.
The first step is to surround the offending area with masking tape to prevent too much filler being spread. My preferred mud is Bondo Glazing and Spot Putty (more on this in a bit)
I use a toothpick and force putty into the gap
Immediately remove the tape and with a Q-tip lightly coated with nail polish remover, start removing excess putty. This is the key, don't let the mud start to set
The end result without sanding
This is the nail polish remover I use. I have also striped the paint off of entire models with this.
The Bondo, with Tamiya bottle for scale.
"But I use Squadron Green Stuff. Will it work with this?", some may ask. The answer is yes and here's why. Green stuff is actually rebranded Bondo which I found out about on another modelling site. So I head over to the 3-M website and sure enough, Bondo is also sold in a green tube. The difference between the colours is working time which is only a matter of minutes. It also comes in white. Now here's the kicker...Squadron Green Stuff sells for about $8.50CAN for a 65g tube. Bondo Glazing and Spot Putty sells for about $9.98CAN for a 128g tube, prices vary of course depending where you get them. A word of warning about the nail polish remover. Some have said it will melt plastic but as I have said, I have removed the paint from four models without incident. I use it sparingly and if I feel I've used too much I immediately rinse with water