Obviously this is only practical if the main halyard only receives minimal adjustment. On many older boats the vang is cleated at the base of the mast on the vang tackle itself. It is worth rethinking the vang so that it is double sided with swivel cleats mounted on the coach roof. This system will allow on the rail adjustment when reaching and places the cleats closer to numerous crew all of whom can be called upon to make an adjustment. There are no hard and fast rules other than it must be easy to adjust and the operator must be within talking earshot of the trimmer.
Many boats have the pit as the area where the spinnaker sheets are trimmed from.
The pit winches normally have two main functions. They are halyard winches upwind and spinnaker sheet winches downwind. This presents a dilemma in that for halyard winches we are looking for low geared small adjustment drums, whereas downwind we are looking for fast line speed, high geared rapid trim drums. Both of the leading winch manufacturers have come up with a similar solution. Both have produced a hybrid winch capable of fast line speed on its bottom drum, and slower finite adjustment on the top drum.