Well, it seems my view of things is always a tad different. But here is one more idea from the certified oddball.

We used to fly at a community college parking lot. It was surrounded by trees. On the south side, 100 foot pines stood about 150 feet from the lot. We had the choice of making a tight pattern inside the tree line or coming over the trees, watching for our shadow to let us know when we had cleared the tree line and then decending. Either way, everone that flew there needed to be very proficient at slow flight. Slow flight is flying around at a very slow speed with the nose of the plane at a high angle of attack and carrying a fair amount of power. Suprisingly, when members of a nearby club came to visit us, they were unable to get their planes back into the field. Many were rescued by local pilots that were expert in the technique and very familiar with the field. (So, unless the situation demands it, most people aparrently don't practice or even know about the technique) I am reminded of that situation every time I hear a story like yours. The first thing I question is wether or not you are aware of the slow flight technique and using it to land in tight fields. Stiks in particular are very capable of slow flight and landing in extremely tight fields with short runways. It is possible that you might over come the situation with technique alone and no modifications. But if mods are ultimately required, my first instinct would be the addition of flaps, not spoilers. Although slipping is effective, (and fun), flaps will allow the aproach to be completed with greater precision. And flaps tend to make a plane feel rock solid at low speeds. And they effectively increase the washout of the wing by a factor of "alot", making tip stalls unlikely. Spoilers, generally aren't something you want deployed on short final. They are used enroute as speed brakes, to increase decent rate, and are generally deployed after touchdown to kill lift, avoid bouncing, and increase braking. But on short final, they can mislead you. Its difficult to sense how much elevator remains for round out and flair and they may overpower your ability to do either.
Anyway, another 2 cents worth.