first, does the cab have a flat finish or gloss? that can make a real difference on decal adhesion. Gloss is the better base. Microset is to help the decal snuggle down, but if it's curling then the solvent may be a bit too strong for the brand of decal. you can dilute it some with water which can help minimize curling. Hope this helps some. :)

Bill

Hi Roman,Bill,all,
As Bill said, a gloss surface is a must in which to apply decals on.
A few other things:

The decals themselves,how old are they?How/where did you store them?
For long strips I ALWAYS apply a coat of MicroScale decal film (MI-12) over them.Let's this dry a few days.
Always use distilled water to soak the decals.
Cut with a hobby knife as close as you can to the decals.
Soak in the water,it will curl up and then relax.
Have a soft brush in Micro Set and then apply that to the surface of the model.
Remove decal from water and gently rest on paper towel to 'wick'away excess water.
I use both the brush in Micro Set,tweezers and the hobby knife(those for the backing paper) and use plenty of Micro Set,slide the decal into position.Work in with the brush/knife until you get it into right.Let this dry! A few hours, overnight,...
Next,use Micro Sol to further soften the decal and make in snuggle down into the suface.Let it dry!
Last step: I use Walthers Solvaset,which is stronger than Micro Sol as a final coat.
Then finally seal the deal with a clear cote.

Dr D