I think if you ask the pros on this subject, you'll find out that painting the stripe area is the worst thing you can do...for several reasons.
First of all, as I understand it...
(and to those who think I don't pay attention...listen up),
...the original has been "Acrylic Coated" along with the rest of the exterior...and you would be painting over that; the bonding of the two is "iffy" at best. (read below)
Plus, in my humble opinion, painting anything that is not able to be sanded well and prime coated, and sanded again --- WHAT A "BOTHER"!!---is troublesome, at best.
The proper use is a stripe called Vinyl Clad, and if you ask for it by name at that place mentioned in this Thread..or ask Andy at InlandRV (on this Forum also), you can find it sold by the foot I think. I'm very close to ordering mine for "Bear"
Anyway, I am a professional designe, and deal with professional painters every day, and I say painting is to be done ONLY when you don't want to do it as a "remedy". And if you do want it for that...be sure you do it RIGHT...and plan for future "re-dos".
Somethings just should not be compromised...
HAVE YOU EVER SEEN A POOR PAINT JOB (the wrong paint) used on the "Under Belly" of an Airstream...it is GAWD-AWFUL !.
In my way of thinking, the stripe would turn out to look pretty bad too, UNLESS you FIRST OF ALL taped off, then sanded well, then prime painted with an OUTDOOR MARINE basepaint, then SANDED again, then a BASE coat of your BLUE colour in another OUTDOOR MARINE paint...SAND AGAIN, the the top coat of a VERY SHINEY OUTdoor marine coloured paint AGAIN. Then, a TOP TOP coat of an outdoor CLEAR finish---like Acrylic.
The problem with all of this...is how do you get it all off when you want to REDO it? A mess! You canNOT remove the old prior to repainting it. And this would be a definite situation in a few years with the UV rays getting to it.
I personally will just get the "Vinyl Clad" from a supplier...and pray the next time I need it it's still available.
(Sorry...a little more than 2 cents worth)...