Traveler
I agree with MArk. A longer traveler is more effective because it provides a larger range of adjustment. A short traveler on the cabin will have the same effect as a long traveler on the transom, because the traveler controls the angle of the boom to the centerline of the boat. If you are sailing upwind on a constant heading, then the traveler controls the angle between the boom and the apparent wind, i.e. the "angle of attack" of the mainsail. The traveler is a "pure" control. The only thing it changes is the angle of attack.The mainsheet also controls this angle but it is not a "pure" control. As you sail closer to the wind and sheet in more, the mainsheet starts pulling the boom in less and starts pulling it DOWN more. This tensions the leech of the mainsail and closes it, decreasing twist, increasing weather helm and possibly increasing heel as well.By using the traveler instead of the mainsheet to control the angle of attack when sailing close-halued, leech tension is kept constant and weather helm can be controlled. The sheet and traveler can be adjusted together to fine-tune mainsail trim.I added a traveler to my H23 last year and it has improved my sailing considerably. I would definitely recommend it. Even a short traveler is better than no traveler. Good luck. PeterH23 "Raven"