I don't know PSP very well as I use Corel Draw 11 for all my decals, but maybe this will work for you.

If you type out your words and then flip them 180 degrees, and then form it to the curve, you might end up with what you want. I'm just guessing here, but it might work.

Corel is really a much better program for decals as it is vector based rather than raster based. In Corel there is a tool that will put text on a curve any way you want to set it.

If you would like to see some of the decals I made for scale R/C models go to

www.heavydatehobbies.com I made all of them for R/C, but have done my own rocket decals as well.
Hope that flipping trick works for you.
Hans