1. Original Trentec setup gives you the (slightly) lowest stack up. The sheet runs through one of the large holes in the car. I always thought friction would be an issue with this setup but I don't have first hand experience. Upgrading to a smaller diameter "high tech" sheet might be a "kewl" solution.

2. Hobie lo-profile car/cleat. Nominal stack up difference compared to the Trentec. This system is very similar to the integrated track system used on new H16s.

3. Trentec car with a turning block on top (courtesy of Hobie 1616). Inventive idea that I have not seen before but not low profile. Similar stack up to the second generation Seaway system.

I agree with Matt's recommendation of the Hobie 1075. I had a similar system on my '82 H16. I really liked the jib sheet cleat on the car, using the cleat on the cross beam to control the traveller. With the Trentec system you use the cleat on the cross beam for the jib sheet and add another cleat (usually a lance cleat) for traveller control.