I don't know if I am that brave to use a marker on the windows Jessica!

I don't think there is that must decal wise loose on the model though; I have used Solvaset before and you are correct it works fine. I may go ahead and give all the decals on the 73 a dose of it anyway. It generally works on those though decals.
I take heart that a 1/72 scale Piedmont 737-200 is being released, although I would enjoy seeing the old Blue and Red Piedmont livery done by someone again. The decals I used were probably 20 years old from the old ATP company that is now out of business. Thanks for your suggestions.
One thing I would add, I had to mix some blue and white together to get the correct shade and touch up the decals where they bled. May do some more of that work soon. Russell