My set up is similar to that suggested by David Tyler.  The deck sheet blocks are attached to a horse about 400m above the transom.  There is an athwartships alloy tube 400mm above that to stop the sheet flicking up and strangling the windvane.  This used to mostly happen when I was tacking and the boat was pitching a bit, with the wind blowing the slackened sheet aft. 

I have a solid roof over the front half of the cockpit, and the sheet slides over this when gybing, keeping it clear of everything else, as long as it doesn't droop down and get under the aft corner of the roof, forcing me to heave it over by hand.  To stop that, last year I fitted alloy tubes that run from the aft corners of the cockpit roof back to the dinghy davits, over which the sheet lies.  Now I can gybe with a slack sheet, though I only do this in lighter winds.  In stronger winds, I adjust the windvane for the new course, push the tiller with one foot to speed up the gybe, then heave mightily on the sheet tail as it slackens, to take as much slack out of it as possible as it comes across, leaving the sheet cleated and flaking the tail down on the cockpit seat beside me.  It works, but I am a bit puffed afterwards! 

I think I could now gybe with a slack sheet even in strong winds, unless the sail is reefed.  When I reef, I do not tie the battens down at the leach, or have a fan-up preventer fitted (planning to work on that again this year), which means there is a risk of a fan-up when gybing with a slack sheet.  Hauling in on the slack reduces this risk.  One thing we are all agreed on, if there is anything the sheet can grab it will, it is like a naughty monkey!

As an aside: for short-handed passagemaking, where you are likely to be sleeping below with the boat self-steering, tying the batten ends down when reefing, or having a fan up preventer, is highly desirable, as there is always the chance of an accidental gybe, which could cause a nasty fan-up.

Hi Mark, There will be others who will no doubt respond with more technical expertise about sheet angles, and I guess Practical Junk Rig would be a good source of information on this. However having owned and sailed a junk rig boat for 10 years now one thing I have learned is that the sheet will catch on anything it can, there is just so much of it. It will easily catch around a tiller so changing from wheel to tiller steering may not solve this particular issue! Over the years I have learned some techniques to minimise snagging of the mainsheet. When hoisting or lowering the sail I always have the boat at an angle to the wind where the sail and bundle are not on the centerline of the boat, but pushed out to the gunwale on the port side, (sail on port side of the mast). Once I learned to do this I dramatically reduced the number of snarl ups. When gybing I pull the sheet in tight before gybing, and then once the sail has swung over past the centerline of the boat I allow the sheet to run out very quickly. I know there is a school of though that says you should gybe 'all standing', but there is no way I am going to do that with my 53 square metre sail. I have also fitted a substantial Bimini frame midway along the cockpit which also helps to keep the slack sheet up high away from things like the tiller and the crew's heads.