downunder

Unfortunately you can't really have the lines inside the wing because the CG of the model will be located well above the wing which would cause the model to fly rolled outwards. A couple of ways to avoid having large slots in the fuselage side would be to use a circular bellcrank where the leadouts wrap around the bellcrank and just roll off it with control movements. Another possibility is monoline as used in speed models but it'd be worthwhile building a trainer to get used to how it all reacts. What I'd do though is to use a quite large bellcrank, at least 4" but the bigger the better. That way the variation in line spacing from neutral to full up/down at the bellcrank could be kept to a minimum.