Thank you for your quick replies 😄

@Watkins
Yes, a Shelling plugin would be great 😄
Skaling will work for cubes for example, but notas soon as there are shapes with curves or such. The walls get different strenghts, and the smaller object might penetrate the walls from the larger object ( http://www.nottoxic.com/wapcc/ae/aqua/curvedresizedsketch.png as a simple sample, but in this particular sample I could just draw a smaller tube).
I do not have a specific sample as I mostly try to hollow the seperate segments now before 3D printing, but especially when working with existing models it would be neat to have a shelling tool in sketchup.

A tool like in photo editors such as erode & dilate etc. would be neat.

@d12dozr
Hi Marcus, thank you for the welcome.
I'll look into the push/pull tool, looks like it at least makes the manual process a lot easier 😄

Ah well, if it all was so easy that no work was involved, there would be no challange 😉
Fixing "Han Solo in Carbonite" with Sketchup which I found at Thingiverse was a challange though and pure madness.

http://www.nottoxic.com/wapcc/3dd/alumide/med_P1070972_t.jpg

http://www.nottoxic.com/wapcc/3dd/alumide/med_P1070974_t.jpg

There I really just copied and scaled a copy, but had to model and cut a lot manually... As there was a deadline for printing with alumide, I had to rush it a bit.
http://www.nottoxic.com/wapcc/3dd/alumide/med_P1070974.html

Similar here;

http://www.nottoxic.com/wapcc/3dd/alumide/med_P1070978_t.jpg

http://www.nottoxic.com/wapcc/3dd/alumide/med_P1070979_t.jpg

Only the flat version printed, I tried to simply scale a copy to make it hollow, but a few parts turned out to be too thin to be printable.
The initial version should have looked like

http://www.nottoxic.com/wapcc/ae/aqua/ae3dDone.png
to replace the stolen car emblem of my GF's car 😉

For square shapes, Sketchup & Shapeways rock my socks though...

http://www.nottoxic.com/wapcc/3dd/med_P1070957_t.jpg

http://www.nottoxic.com/wapcc/3dd/med_IMG_3611.html
This little thing will hopefully fly next week, as soon as the TT Copter Control arives 😄