If you ask a stupid question, you may feel stupid; if you don't ask a stupid question, you remain stupid.
However, this isn't a stupid question.
If you are not racing or otherwise trying to go as fast as possible, leave them 3/4 of the way inboard.
If you are racing, from my experience:
Upwind, pull them as inboard as possible without backwinding the main. If the slot (the space between the jib and the main) is too small, wind going through the slot will indent the main the wrong way, ruining your sail efficiency. Start with the travellers in, then put them out until the main stops indenting at the luff, and then put them out a little more than that. The amount you need to do this depends mostly on the speed of the wind - high winds will require a bigger slot than low winds.
Downwind, travellers all the way outboard. If winds are very light, you won't have to bother with this, as the crew will probably be holding the jib at the blocks or the clew to reduce the weight on the sail.
Adjustable travellers with the blocks, cleat and line make this much easier, though you will still have to let up on the jib sheet to be able to adjust. Spring-pin travellers are trickier to adjust since it requires the crew to be right there. Unless you want to seriously kill speed (or the wind is very light and your crew is over on the leeward side anyway), you'll have to do all adjusts on the tacks.
Anyone else? Thoughts?
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