Be careful using Eternabond on new RV roofs as some RV owners have reported it can void their new RV roof warranty.
Whatever you add up on the roof don't make a dam (lake effect) for water to sit such as piling up sealant on sealant or Eternabond laying over a pile of sealant.
Eternabond is great stuff when applied properly. Check out some of the many youtubes on installing Eternabond. Just be sure and seal the edges with Dicor (or similar products) like the pros do it. Looks much better and it seals the edges from water intrusion.
Unless the OEM sealant is lifting or cracking I wouldn't make a mess up there.