Patrick, It would be great if you shared your models. Point us to where you have them even if it is on rc-sim.de.
I would be happy to help with putting an image map on your model. Please see my other image maps for a sample of how I usually do this.
To merge a wing with the body requires aligning the parts or just moving the wing where you want it.
In my early models, I did not know how to align points and it really makes things look a whole lot better.
1) Unlock the two or more parts whose points you want to align.
2) Select the points you want to align.
3) In MetaLE, click on the <Selected> menu and then the <Align vertices> menu.
4) MetaLE will open a dialog box with X, Y, Z rows and will guess which axis you want by checking the Apply column
5) If that is what you want, click OK.
6) If not, you may want to click all 3 axis, just 2 axis or re-choose a single axis.
If it messes something up, used Ctrl-Z to undo the alignment.
-- ggunners