For more control and to avoid need for winching, especially on coachroof mounted mainsheet tracks, a two-speed main sheet system may be the solution.
The following pictures show the BSI "Easymatic" system fitted onto a Sun Odyssey 37.
Due to the doubling of mechanical advantage, winches are not normally needed to pull in the mainsheet.
An extra set of halyard organisers have been stacked above the original set.
The sheet end may also be led back to the wheel pedestal to allow the helmsman to dump the main in gusty conditions.
This should be particularly useful on the SO 34.2 and other Jeanneau's where winches are at a premium, for example when have dual use for the primary Genoa sheets.
A potential downside is that with the significant additional length of sheet required, this needs to be carefully coiled and handled. It may be long-spliced form a continuous loop.
Spinlock PXR "Powercleats" have been used (max sheet dia is 10 mm) which enable the sheet to be released easily underload.