Will,

If it's great downwind then twitchy upwind and you haven't changed the downhaul setting much it sounds like you are overpowered upwind.

Try cranking the downhaul on a bit more, put the outhaul on fully then let it off a bit and play the mast rotation.

Like you already said nothing is accessible from out on trapeze so with a few mods you should be able to reach some controls with relative ease next time out.

Regards,

Peter