Thank you all for the suggestions.
Someone suggested useing the Herc wings and attaching the engines and rotors further up the wing. This again I considered so I found the `sweet spot` and it looked good from a with point of view.
The major issue with this was the thinkness of the wing at that point. In my eyes it just would not look right going out from the wing root. ie, thick, getting thinner and then getting thick again. I`d also have to look at fitting outriggers to support the weight. Again this was going to be too complex IMPO.
So it came down to this.
I`m going to just cut down the middle and then `graft` the two pieces on top of the existing Herc wing routes. This way it will cover up a lot of the part that don`t need to be seen while adding a bit of length. I can then add a few bits from the spares box like one half of a fuel tank to cover up any gaps, but it should still give it a stream lined look without covering the whole thing in filler.
It won`t be a pretty build, but the end result might just be worth the hassle.