Here's what I did:
In the end I figured it was worth the $23 to try vinyl stickers from https://www.bannerbuzz.com/
They have a tool that let me create a banner that was 3.75" x 240". (Yes, 20 feet long.) The tool let me create long stripes of whatever color I wanted, so I "guestimated" what would look good as a replacement for the top stripe, ordered it and had a friend help me lay it down. Pictures attached, including one of the design tool with the stripe.
First, to be clear: I DID NOT strip off the old stickers! The original decals/pin striping was so sun deteriorated that when I took my pressure washer to the RV (even being careful), the slightest pressure would make the colored portion of the original decals come flaking off leaving the adhesive layer behind. I had no intention of buying a scrubbing disk and trying to remove it after what I was was required from watching videos! A few original spots would still be left behind, so I was fully aware that I would be placing a sticker on an uneven surface. I'll remind you: $25!!!
Well, it worked great in my opinion. I stupidly forgot to use the soapy water and squeegee technique to put the decals on - so it's not perfect. Close up, at an angle, you can see the imperfections, but I wanted it to "look good from 10 feet".
The biggest problem- one that might cause me to peel this off and try again with a new design - is that I *stupidly* thought that the company making the sticker would have machines that created nice clean edges. They didn't. I chose a white vinyl background, but made the blue color stripes stop and start on the edge of the strip. When they were cut, they weren't straight lines, so in the photos you can see how the top and bottom edges don't look straight - this is because the sticker wasn't cut properly. ($25!) On my top edge, the top and bottom pin stripes looked great - never peeled off - so I had measured and designed and ordered a strip that would fit between these two existing stripes. To be fair, their tool makes reference to a safe-zone that I should not have put a design on. The white of the vinyl decal would have looked almost invisible against the white of the RV, so I should have left a white bottom and top edge.
In summary, this $25 experiment looks so much better than the old peeled decal that I'm going to keep it this way and see how it holds up to rain, wind, etc. I'll report back.