Ah man, you should give it longer!
It took me a little bit of adjusting to get used to 5, but it's really not that bad. If you can learn to play 4 strings, you can eventually play 5 and particularly if it's a right hand issue you can practice that out till it's no longer an issue.
Another thing I found with my Shuker, which I am sure is typical for any luthier built bass, is that it took a good 6-12 months of owning the bass for it to start to feel worn in and as time passes, my bass feels nicer and nicer to play and more and more like a settled instrument.
I really think you should reconsider before selling this one up dude, especially if you've waited all that time for it to be built. Anyone can get used to playing an extra string really, I've got fairly small hands and have no problems with it and while I can find my way around a bass pretty well, I'm not an amazing bassist!