Hi Matt,
Is the DFS trike base with the 15m North Wing a factory supplied wing + trike base combination?
The only time you should adjust your control frame forwards or backwards WRT the wing is if you are using the wing on a different trike base with different geometry.
That is, in flight, the range of angles about the hang point from horizontal (or vertical) from pilots chest to front brace tube in the arc your control bar will move in is different to the trike base the wing was designed to be used with. I would normally measure these angles with the trike base suspended from the hang point.
If at all possible, you should always consult the wing manufacturer before making any changes and be extremely cautious with the first flight, eg, Whenever I put a wing back in service after any repair the first flights consist of getting the trike almost up to stall speed so that only the nose wheel will lift and checking there are no adverse roll characteristics in the wing while the back wheels are still on the ground, 2nd run no higher than 10ft AGL progressively testing pitch control only and landing again before the end of the runway. The longer the runway the better, 2,500ft or more recommended. Runway length should not be a problem in the USA.
I think I would have touched on this subject in this thread.
http://www.recreationalflying.com/forum/microlight-trikes-aircraft/25428-buzzard-trike-restoration.html
Finally the disclaimer. The above is only how I do it. I am not an instructor. I am not an Aeronautical Engineer, I am not a licensed aircraft mechanic. The regulations in your location may or may not allow you to do this yourself and it is your responsibility to check.
Cheers,
Glen